The brand name is actually spelled Sculpey, with an E.
I don't know for sure what Christian uses, but I prefer the third version, called Super Sculpey, for my own sculpting projects. Regular Sculpey is white and the texture is sort of creamy. Super Sculpey is pink and feels more like plasticine modeling clay.
The directions usually say to bake it, but I prefer boiling it to 'cure' it... that is, to harden it and make it permanent. I especially prefer boiling white 'Sculpey' (version 1) to baking it, because it stinks up your entire kitchen with a smell like burnt salmon. When boiled, there is no odor.
Once cured, Super Sculpey can be sanded, painted, etc.
One of the cool things about it is that there is no shrinkage when it hardens, so if you're making a piece that is supposed to attach to an existing figure, it should fit back on perfectly after it is cured.
Alex