head mould help??

Once you get the hang of pulling off the sculpey without warping it, that should work great

There are a lot of products out there that can help you mold and make things like that.

You can use the more rustic way that I sometimes use if you're only molding part of the head (and are a cheap-skate, like myself). Get a wad of Sculpty and press the face into it and pull it out slowly to make the mold. Harden the Sculpty. Zap the Sculpty mold with some sort of non-stick spray. Even cooking spray works fine, and press in the epoxy putty (or whatever molding material you're using) and leave it in there to harden. Maybe stick a toothpick in there or something to help you pull it out.

Stick it on the head you want and fill in the seems with more putty, sand down and you got it. Easy.

It's pretty great. I used it for Boba Fett's helmet, but I put too much pressure in the mold and stretched it with the Apoxie and Bullseye's head so I had to sand down the excess a lot. But that's how I made Boba Fett's jet pack!
I don't really recommend using Apoxie Sculpt in it. I think you need something closer to a liquid so you don't accidentally stretch the mold and distort your cast.

Reusuable would be good because you never know what parts you're going to want to duplicate!

I bought this stuff called Elastack from a guy on eBay. It's a reuseable mold making material that you heat until melted, pour over the item, let cool and pull the item out and pour in what you want. I got it from a guy on eBay that goes under the name of iplasticsnyc.

No clue

I'm sure there are tutorials showing you how to make molds and what materials to use.

The "best" way to make a mold (the container) would be to make it out of silicone-rubber since it flexes so you can pop out the casting (the thing you made in the rubber mold) easily.

sorry I got mixed up

Why would you want your MOLD to set like plastic? Wouldn't it be hard to pull out what you cast in it?