This is a FANTASTIC thread. I've always been curious about casting, because I just couldn't get my head around the process. This has laid it out for me and let me know two things: One, I should never, ever try to do this. Two, I should never , ever try to do this. Your work (at every stage) is outstanding! Thank you for sharing it.
It's not as hard as it might look. What I'm doing here is making matrix molds, solid casts and rotocast parts. This is about as complicated as this stuff gets. The easier versions involve just making block molds. Technically much easier to achieve. If you'd like to know more, I actually wrote a book with a pretty detailed section on molding and casting. You can get it on Amazon here: Make: Props and Costume Armor: Create Realistic Science Fiction & Fantasy Weapons, Armor, and Accessories: Thorsson, Shawn: 9781680450064: Amazon.com: Books