I've made a mold for my robot hands, I'm just using whats quick and and available so it's made out of silicone. Probably not ideal as its going to be a silicone on silicone mold, but I'm assured that as long as I spray on lots of J wax (or whatever release agent in the cupboard) it should be okay.
I didn't mix some of the catalyst into the silicone well enough so it didn't go off. Luckily one of the more experienced maintenance crew was able to save it (you can see the colour difference in the pink half). Also, in my rush, I left the registration balls in! - it'll be fine
To save time I'm only making one hand which should work on either side