Step 10: Small "metal" Pieces: Wonderflex
The methods I ultimately used for the small "armor" pieces are super easy, totally non-toxic, and cheap. The photos are of the boot caps and the armor pieces which go on the front of the jacket.
1) Base: I made the smaller pieces out of a product called Wonderflex. Wonderflex is a thermoplastic that can take complex curves fairly well. It's easily heated to form with a heat gun, or an embossing gun or hair dryer. While hot, it feels basically like stiff fabric, so it's best to form it over a positive of some kind; if just slightly heated, you can bend it with your hands. When cooled, it will keep that shape. For the boot caps, I actually managed to heat it over the boot itself with my foot in it by heating it to soften the material first, and then pressing it over my boot.
2) Raised details: I did the raised details with a hot glue gun. Hot glue is a thermoplastic also - liquid when hot, cools into a plastic.
3) Finishing: Because Wonderflex has a texture to it, similar to the surface of duct tape, I sealed it with 6-7 coats of Mod Podge and then wet-sanded it lightly to get a fairly smooth finish. It isn't perfectly flat, but neither is beaten metal.
I used different techniques for painting the different pieces but it really looks best if you don't just spray it a solid color. A warning - make sure the paint and any topcoat you use can flex with the piece. Otherwise, if you have something that will be subjected to frequent bending, it will crack. I didn't test this thoroughly enough.