I would actually go more ridgid, at least to create a base to mold something soft on. My experience comes from theather where masks were worn 20 hours a week for 6 weeks. Molded to your face perfectly is the most comfortable thing, even over soft strechy things
. Yes, I said a hard plaster mask is more comfortable than a strechy rubber one if it's custom fitted
Knowing how a professional would make that originally helps. Basicly they would have made a plaster cast of the actors head, then used that to make a rubber/ silicone/ latex mask. You can't 'draft' off a natural human face because it is soft, the chemicals are sensitive when liquid etc.The nice part for you is: 1) it's only half a face, you could probably do it solo or with untrained help, 2) plaster is pretty cheap & half a face uses less. It's the latex or rubber that gets expensive fast, but that's where you get creative
Use plaster cast material (available for big $$ at crafts stores, much cheaper through medical suppliers) and make a mold of your face (put staws in your mouth for easy breathing).
Now you have two choices:
Do lots of layers to make a good strong mold. After removing paint the inside with several coats of varnish. Use straight plaster to make a mold of your face. Now you have something you can use to mold your funfoam, rubber sheeting, plastic strips , etc on & make it perfectly snug & wearable.OR
leave the original mold at about 4-5 layers (that medical casting stuff is pretty thin) and cut it down to the shape you want, paint, glue etc & use it directly to make your mask.
What, you thought being an actor was easy?