So.. this is what happens when the huge dork, Jax is wandering around Micheal's Crafts to restock supplies, and stumbles across an interesting product with costume potential...
The product is Crayola Model Magic. It's this spongey clay stuff that dries into a semi-flexible, semi-squishy state. This stuff has MAJOR costume potential. I originally tested it by making that set of horns, which I gave a thick coat of heavy gloss paint, but then the dork in me got a neat idea to experiment with, so I picked up some cheap, blank plastic masks too. The goblin is finished, all painted and varnished, and the bugbear is a WIP. He needs paint and fur, when I get the time. Each mask and the horn set took one 4oz bag of the stuff, which cost me $3.50. Not bad. Now, it dries pretty light, and as far as durability, this stuff is okay. Thin things like say.. the ears on the masks probably couldn't take much abuse tho. Overall, I'd suggest using it on things that won't have to deal with major abuse. Noses with a heavy varnish, mouths and small horns. Maybe larger ones if you use an armature first.
Really fun to work with! I also picked up some of this amazing stuff called 'Wonderflex' (
http://www.cosplaysupplies.com/wonderflex/wonderflex.html). Plastic sheets that soften with heat, to where you can shape them. Great stuff, but expensive. Hardens like friggin steel, though to get a smooth surface you need to work on it.