Try Magic-Sculp Black Resin. It's a great product, you can push it into latex molds or you can shape it free hand. it's really great stuff, it comes in a few different colors but for the pack black is the best. anyways, it handles like clay, but it dries a black, semi-glossy durable resin.
As for mold making, you need some roma plastalina clay to carve an original (the medium hardness is good) and some moulding latex. also, when you get the resin, be sure to order a mold release spray with it.