Hi and welcome aboard! I’m actually working on the exact same thing at the moment. I usually work with resin to cast parts, but right now I’m looking for an alternative material for parts I only need once.
So far I ordered blue stuff, but it hasn’t arrived yet. I will make molds with this molding clay. As casting material I decided to use two component epoxy clay. I never worked with epoxy modeling clay before and still need to find out how hard it cures. The Epo Putty arrived today. It’s not the cheapest with about $80 per kilogram. And it’s actually a very efficient two component adhesive. I saw a guy on YouTube who uses it as modeling clay and recommends it. Another epoxy modeling clay comes from Milliput.
You can find tutorials on both blue stuff and epoxy clay on YouTube.
Now, I have no experience or knowledge on the production of rubber. Therefore I also don’t know which material Hasbro use for the Clone Trooper helmets. If you don’t want to use resin for casting, these videos might help you. If you live in the U.S. you’ll easily find the used material.
What I can is recommend silicone to you for making the molds.
The rubber used in the video is also based on two components. I’m sure there is also a softener or hardener for such rubbers that can be added to adjust the consistency of the cured product.
I will let you know as soon as I find out more. As I said I’m looking for other materials than resin at the moment, too, and keep your request in mind.
The combination of these two videos might be helpful to you:
I just found this channel myself after reading your post. This puppet is a little weird, but this guy knows a lot and has many more videos on his channel.
Best regards from Germany!
- Philipp