Using some old kit parts 1/72 scale I made molds to build various resin Nieuports 11, 17, 23, 27. Using Testors decal paper I made custom decals for my planes. Its fun! I also made a mold to do Halb CLII 1/72 done all by hand for which I am going to re work again. Also Spad 13's. Soon some Fokker DR1's as well. Here is a list of products and where you can buy them in the United States for scratch building resin for which I have found work best:
West Marine Boaters Polyester Resin : Store, West Marine : cost $12
Evercoat Mold Release: Store, West Marine : Cost $10
Super Sculpey Sculpturing Compound (this is a chip resitant compound used to make molds and is a better grade than the regular Sculpey Compound): Store : Michael's Crafts or possibly other craft stores. Cost $7
Evergreen Plastic: Store, about any hobby store may carry their scratch build plastic in various rods, sheets, etc..
Decal paper: Testors, $7