Ah, I hadn't read about using a silicone mold and a mother mold, thanks for that! Your post really helped clear some things up.
After looking at the shape and design of the model again, I've decided to try to make it be able to go on in one piece, so that eliminates a good portion of the complexity. I also decided to make the gold mask out of the Sintra, so that makes it even simpler. Time to find the time to get started!