I was faced with a dilemma... I needed some hands fast, and didn't have time to sculpt and cast a pair. They needed to be weatherproof as well. These fit the bill.
Materials needed: self-adhesive foamcore (or regular foamcore and rubber cement), liquid latex, utility knife.
Step one: using the template you have dangling from your other arm, trace your hand onto the foamcore. Cut out the hand with the utility knife. Believe it or not, the tough part is over.
Step two: Decide where your joints will be, and bend the foamcore appropriately. Pinch the sides of the foamcore between the joints to put a slight curve in the finger parts. Cut several strips about 3/8" wide x 8" for tendons.
Step four: Apply tendons while bending fingers into the desired position.
Step five: Build up the area in the heel and ball with more cut pieces to bulk them out.
Step five: Cut pieces for knuckles. Not shown in this series are the row of tendons applied to the back of the hands, which really sell the effect.
Step six: Pierce the wrists on a skewer, and dip completely in a bucket of latex. This step can be substituted by brushing, but dipping builds up the areas better and faster. I use RD-407 mask latex. Allow to dry for several hours, and catch any stray drips that form at the fingertips.
Step seven: Repeat step six until enough material has built up to flesh the piece out. Remove from skewers and plug the remaining holes with latex. Paint and seal.
I'll have finished pics in a day or two.