Have you made a silicon mask (disguise)?

I’m sorry I haven’t made one of these. But hopefully this and this might help.

I’m afraid I didn’t find anything on silicon.

A one piece mask won’t be very convincing. Old age make ups are the gold standard of the make up industry, ie they are the hardest. The highest quality ones are made of small overlapping pieces sculpted over a mold of the actors face. They’re probably cast in something like silicone which is more luminescent than latex. I wouldn’t attempt something like that without a solid background in the craft, its expensive and takes experience. You might look into more old school theater make up techniques. The classic one is to brush egg over the skin. It will pucker and wrinkle when it drys.