I had mentioned resculpting any areas that need fixing and sculpting any additional features you might want, like an autopsy scar or split open chest, etc.  Do this by adding or removing clay to the desired form smoothing it out with alcohol then add the desired texture.
Cap off the two ends, i.e., neck and waist openings using the white clay EM-210.  You want these end caps to flare out from top to bottom, so that they are wider at the bottom. Smooth the caps out with a damp sponge.  Work your way around the sculpting by filling in between the bottom of the torso and the table that you are molding on.  Fill this in with white clay and flare out the smooth.  This will prevent the plaster mold from wrapping under the torso and leaking behind it.
Spray a few light coats of crystal clear on your sculpt and let it dry.  Spray on a light coat of that wonderful dulling spray.  Fill each of your three two gallon buckets 1/3 full with cool water.
By hand, sift in Hyrdocal slowly until that water has absorbed enough plaster to make it look like a dry cracked riverbed. Do not stir or agitate this plaster!  Sift in plaster to the two remaining buckets. Do not agitate.
Glue the bristles into the handle of the two inch and one inch chip brush.   Do this for your assistant as well. Mix up the first batch of plaster and stir for until smooth, let the plaster cream.  Pour some on the top of the torso, spreading it with the brushes to get the plaster down into the detail areas and avoid trapping any air bubbles.  Pour some plaster into another container for your assistant. Continue to pour and paint as the plaster thickens building up and even coat.  As one person continues to work the plaster, the second person should mix the second batch before the first one sets.  Mix until smooth and paint on a thin layer.  Dip in your 6x9" strips of burlap and squeegee them out between your fingers. One person should do this task and the other person should apply the strips.  Lay the burlap on and smooth out use enough pressure to smooth them flat without trapping any air but not so much as to crack the first layer of plaster that should still be wet.  Cover the entire surface with burlap.  Repeat this process. You want to apply at least three to four layers of burlap.  Mix the last batch of plaster.  Add more burlap if needed.  Spread plaster all over.  Using the two pieces of 1"x2"x48" wood, lay them from shoulder to waist and attach them with burlap and plaster.  Using the two pieces of 1"x2"x24" wood, lay one piece from shoulder to shoulder and the second piece across the waist.  Attach with plaster and burlap.  Smooth out the rest of the mold with plaster. Your mold at this point should be between an inch and a half to 2 inches thick. The wood will serve as a frame/handle that the mold can rest on and remain level when flipped over.  Let the mold set up and cure for at least two hours. It will need to heat up and cool down completely.  With the help of your assistant and using the handles of the mold, gently flip it over. With a saw, cut the wood handles in the back of the torso and remove them.  Carefully remove the plaster and burlap layer. You will need to "break" this out. Aren't you glad that you kept this thin! Be careful not to damage the mold's interior surface. I have used a hammer and chisel very carefully. After all the support plaster is removed peel out the clay. Use a wood popsicle stick to pry and lift.  Be careful not to damage to mold surface.  Clean out any crystal clear residue with a brush and acetone.  Now you should have a beautiful mold that looks like a rectangular bowl on a wood frame! Gee, you could fill this up with...Latex!  Let the mold dry out for a few days, the drier the better. Tint your latex with proline tints to the color that you want. Mix your tints in a separate cup until you get the proper flesh tone.  I like to use  raw sienna, burnt umber, yellow oxide, red, white and a touch a green or blue to "mute" it. The browns, reds, yellows, and white will create a good flesh tone but it looks a bit too clean, like Barbie skin. The blue or green will grey it out just a bit and make it that much more realistic!  Don't use too much just a few drops.  One cup of tint will color at least 5 gallons of latex. Mix half of the tint into 1 gallon of latex and mix this into the rest of the latex.  Place a drop of this on the outside of the mold and let dry to test the color. If you need it mix in the rest of the tint in the same way.  Don't judge the color of the latex when it is wet.  Latex will dry much darker and opaque, so be careful.  Pour 1 gallon of tinted latex into you mold and brush into the surface detail. Be careful not to trap air bubbles. Cover all surfaces quickly.  Fill up the mold to the brim with the rest of the latex. If your torso is large it may take more that 5 gallons, so have some standing by. Cover the latex and mold with plastic wrap.  It should rest on the surface.  Latex cures by lowering the ph. The dry porous plaster absorbs the water and ammonia out of the latex and a skin starts to form against the mold surface.  Many people think that latex is an air dry cure, this is only part true.  When the ammonia/water evaporates the ph is lowered and the latex cures.  Let this sit for 1 hour or so.  Check the thickness at the top of the neck or waist by brushing the latex away and look in at the thickness against the mold surface. It should be about 1/8" thick.  Pour the latex back into the bucket and place the mold upside down on some wood blocks over some plastic to finish draining.  Let this sit about 1 half an hour.  Flip the mold over and fill it again as this will protect it against thin spots. Let sit fifteen minutes and drain.  Let the mold sit upside down on blocks for 24 hours.  It is best not to rush this.  Inspect the interior of the latex skin.  If there any thin spots, while the skin is still in the mold, brush thin layers of latex  on the thin spots and cure with a warm blow dryer one layer at a time until you have at least 5 to 8 layers.  Do not remove the latex skin from the mold.  You can back up your skin in two ways.  With a rigid backing like fiberglass or soft like poly foam. this depend on what type of stress will be applied to the top of this cast or the space requirements beneath. I will be discussing poly foam as it is easy and a bit more comfortable for the actor.  Spray in some 3M Spray adhesive 77 or similar spray glue. Spray in two layers and allow to dry.  This will insure adhesion between that latex and poly foam.  Paint paste wax on the outside of the mold and top edges.  So that the poly foam will not stick to it.  Do at least two coats.  Measure out the proper amounts of 4 lb. poly foam according to manufacturers directions into two separate paper containers.
Note: Do a test with this material in a paper bucket to see how it works. Different poly foams expand to different volumes, you want to figure out how much you will need to fill your mold plus some. Wrap a 4'x2' piece of plywood in plastic.  Pour both parts of poly foam into a paper bucket and mix rapidly for about 6 to 10 seconds and dump into the mold. Slosh it all around and cover with the plywood.  Do this VERY quickly.  Hold the plywood in place and do not move as knocking or jostling the mold can cause the foam to collapse. Foam should spew out from under the board, so do this on plastic. I often cut a 2" escape hole in the plywood and tape the edges with duct tape.  Leave this in the mold for an hour. remove the board and plastic.  Trim off the excess with an electric carving knife or razor blade. Pull the latex from the sides of the mold inward.  Loosen and remove the torso.  You now have a latex and poly foam replica of your victim's chest that is pre colored!   Your victim will have his shoulders, arms, and head sticking out of a hole in a table etc. while his actual body is resting on a padded slant board or slant chair. To make a seamless rubber to flesh blend on the neck and shoulders is impractical for a haunt in any situation. You would be required to make a more complex mold and use more difficult materials to
master.  In addition to this, it would cost a lot more and take 1 to 2 hours to get the actor
into the rig every time, not to mention the maintenance on the piece.  Good for one shot in a film bad for a haunt.  So with that in mind think, "camouflage".  Restraints on the neck and shoulders can cover the edge and adding some on the wrists and legs with chains will  maintain continuity. A shredded shirt with bits and pieces in the right places. If you are ambitious try some separate appliances with sutures and blood.  Just be creative and aware that you want this easy to get in and out of while still remaining a fantastic illusion. Imagine doing a two hour make up job and then the actor informs you that he has to use the bathroom, it happens on movies all the time!
Scribe out, hollow or dig out the sections of the chest that you need for the prop. You can peel the latex from the poly foam with the aid of some 99% alcohol and carve the foam with a electric knife to the contours needed to lay the neck and shoulders flat on top of the actor and contour down to the table.  Leave enough latex to wrap around the neck and trapezoids muscles as well as into the armpit. You will have to cut away some of the latex to allow this.  Leave as much as possible to wrap around and out of sight.  The sides of the torso Where it meets the table can be covered with some "blood" paint or the actors arms, maybe some surgical apparatus.  You can scribe out a hollow area for things to burst through the torso, leaving at least 1/2" of foam to give the flesh enough body to support itself.   You can cut and mangle the torso add some ribs poking out, a heart, hide a bucket inside filled with guts and blood for the actor to reach in an "play" with.  Add any thing like ribs after you cast the chest.  You can carve out part of the inside and glue in the ribs with a small batch of foam and then cut the skin from outside.  Always leave as much foam as possible for support and to maintain the torso in its proper shape.
Paint with Badger airbrush paints and thin with 99% alcohol. This is the easiest and best formula to use.  It only works with Badger air brush paints.  Use velcro to attach the torso to the table and the stuffed pants that you are using for legs.  Often the first casting is not perfect, and it is always good to have back ups, so cast up two or three you will learn a lot.  Have fun, this is a great illusion.