So I'm going over a list of materials that I've either worked with or will be testing (soon, like this weekend) for making prosthetic makeup and lifelike props. And for me, "lifelike" not only includes "looking good" but often "feels good" and "moves realistically"... which rules out most foams for most props.
Cold Foam, played with it a bit, might be good for static props that don't get handled, or that are viewed from a distance. Hot foam is softer with better characteristics, but too complex to work with for this poor soul.
Liquid Latex, I've used for built-up wounds and stuff but I've never been happy with its stiffness and the difficulty in applying makeup to it. Of course, I've never had the RIGHT makeup, which is changing soon, so I need to re-visit liquid latex.
Silicon, lovely handling characteristics and can be made hard to really really squishy. A pain to paint but has lovely translucency, and should be able to hold punched-in hair nicely. Easy to work with and not very noxious. Expensive.
Foamed Silicon, which I've not tried but sounds interesting. The foaming should give it a softer feel and improve its compression characteristics, which might improve its use as facial prosthetics. Anything that makes a product move with the face helps. Foaming, however, makes materials opaque.
Gelatin, I've used this a bit in the dim, distant past. I'm going to try it again for wounds. Cheap, but melts in heat and with sweat. Sweat you can block with chemicals, but heat... in Texas... yeah. We'll see. Translucent. Cheap!
Foamed Gelatin, like Gelatin but softer, lighter, and will lose its translucency. But still neat!
Squish, or as it's formally called, hot-pour PVC. Cheaper than silicon, translucent, and has good handling characteristics. And it can be made harder or softer, though I've not used those additives. Noxious to work with, since it is worked at 250-300 degress F and smells bad (I wear a breathing filter). Also, has poor stretch and tear characteristics compared to silicon. I don't think it will be very good for prosthetics since it's slightly oily and may be icky for the skin. And it's hard to apply makeup to.
Foamed Squish, just to be cool. I do want to do a test of it as a wound prosthetic. It won't melt like gelatin and has similar cost and feel characteristics. Except the oiliness and the difficutly in sticking anything to it! But it should hold punched-in hair and I'm thinking gelatin won't.
Polyurethane, which I use for molds and the occasionl body part. Can also be made squishy with additives, and while still expensive, is cheaper than silicon.
As for mold-making materials, I've used polyurethane, body-safe silicon, alginate, and the usual varieties of plaster.
I like working with new materials... it's fun! I'll have to write a book or something, someday.