I've been saving chunks of cured platinum silicone from old molds I don't need anymore. Though I did try using silicone caulking to thicken the mold of my 1:4 scale bust, but the platinum silicone started to peel from the caulking first time I de-molded, and by the third casting it was unusable...
I've used Smooth-on "flex-foam" while the mask is still in the mold. Though need to be careful because it releases toxic fumes. But all in all I'd do a combination of both methods. Flex foam to get into the smallest creases and crevices like horns or large wrinkles and give them some support...
Vebo would certainly be the one to talk to as I haven't made my own gloves yet.
I'd say follow this video up until after the demolding and removing your own hand. I don't think silicone rubber will make a good casting to sculpt on, so I'd opt for something hard like plaster, ultracal30, or resin.
The hands are pretty much the same process as the head and feet. the difference is first you make a life cast of your hands, then use clay to sculpt on that. Once the sculpt is done you make a two-piece mold made of either Ultracal30 or Resin/Fiberglass. Clean the remaining clay from the cured...
It looks good in general. If I could make some suggestions.
I would try and remove some extra foam around the snout, roll up some paper-towels and dip them in latex to create wrinkles on the forehead that stick out. I'd let those wrinkles dry and stick, and then cover them with more liquid...
This is the scene people are talking about? I've seen multiple people hold it up like it's a key moment redeeming the whole film ... liked the mandible movement but that's about it. Glad I didn't waste my money seeing it in theater's and instead am seeing more and more snippets on YouTube XD...