1. 16 lbs. plaster of paris.
(8 lbs for the top half, 8 for the bottom. )
2. BFX ballistics gel.
(Check out this Weekend Extra for more details.)
3. Liquid latex.
(In a flesh tone.)
(Does not need to be adhesive.)
5. Petroleum Jelly.
(As a de-molding agent. You could also use cooking spray.)
6. Duct tape.
(I'm going to stop listing this because you should always have some ready.)
7. A cardboard box.
(To add some "fleshyness" to the face.)
Step 1: The Mold (Part 1)
Next mix up half your plaster, which should be about 8 lbs for a hand mold. As mentioned by Jared, use a little more water then recommended. Cover your subjects entire hand and arm (anything going into the plaster) with petroleum jelly. Now pour your plaster into the bo. It should be about 3-4 inches deep. Place the bottom half of your hand into the plaster and rock it back and forth to get it to sink in. Don't put your hand too deep into the plaster.
Step 2: The Mold (Part 2)
Once the bottom half is dry, you can move to the top half. Apply more petroleum jelly to the bottom mold and your actors hand. Mix up some more plaster and place hand back into mold. Pour the new plaster over your hand and the bottom mold. Wait the some amount of time for this layer to dry.
Step 3: The Mold (Part 3)
Step 4: The Hand (Part 1)
Now seal the mold and, using the some cardboard box, and duct tape close both halves of the mold together tightly. Allow for the caulk to dry. Now you're ready for the fleshy filling.
Step 5: The Hand (Part 2)
This process may take some trial and error. The good news though, is that the whole thing doesn't cost much money. Also, once you have a really good mold, you can make many hands from the some mold. Another cool thing is that you can use this same process to mold other objects or body parts.