Which clay can you suggest for making busts and then molding

I think Monster Clay is the best solution I've seen so far, but here is what I want.

A clay I don't have to bake or put in a kiln, but something I can work with before it hardens.
I live in a really hot and humid climate, so will monster clay just melt if I try to use it in the garage?
I like regular clay in the sense of wetting it, but I like the sulfur free model clays because they don't get gunky.


But I want it to be a clay I can make a mold easily and pull out the original from the mold without damaging both. If it's a soft clay I don't mind cleaning out the mold before I do a casting.

Can I easily do brush on molds with Monster Clay?

Monster clay never hardens fully. And you can make a mold on it, and as long as you release it properly you likely wont destroy it. It smooths with mineral spirits.

Monster clay is quite soft when warm. What scale are you talking about?