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.