I've seen people build out Iron Man masks with bondo for Red Hood, but depending on the art you're basing it off of, I think that might be counter productive. The MCU Iron Man build has a really specific jaw shape that you'd have to build away from pretty significantly for Red Hood. The closest thing in shape to the original Under the Hood are stuff, and the way its drawn in Lost Days, to me, is probably a balloon, which you can buy, blow up to size, and then papier mache around. From there I'd take fiberglass resin and paint it on in thin layers, sanding as you go to keep the glossy texture.
As for Damian, it really depends on your sewing skills. His shirt is a pretty basic, fitted, princess-seam set up. I would probably use a stretch twill or something similar to get that heavy sort of look, and just scour JoAnn's or another fabric store for a commercial pattern you can edit for it.