I am interested in hand painting coins and would like to know what materials are best to use.?

This comes under the heading of "making jewelry." Of course you can use cold enamel! Miniature painter of tiny leaden or pewter figures use cold enamel. Believe me the only thing a torch or kiln would do to the soft metals in your coins would be to melt them into slag. I recommend a miniatures' painter's kit, then toss in some of your favorite items, such as the magnifiers, jewelers' tweezers, some nice tiny, soft natural haired brushes (I have a friend who uses one of his brushes with all but one hair plucked out!). If you shop online, Pearl Art is great, but so is your local hobby shop, they are all online, therefore I would refer you to Google's search on miniatures pages�.