Option 1:Blast the prop to bare metal, prime with Interlux Interprotect or a similar barrier-coat epoxy, and then paint with a conventional hard bottom paint. (Although the epoxy theoretically prevents galvanic reaction between dissimilar metals, copper-based paints are to be avoided.) The trick with using a conventional bottom paint (sprays like Interlux Trilux 33 or Pettit Alumaspray are easier to apply) is getting it to adhere, thus the epoxy primer. Although there are options other than epoxy for priming a prop, because of health concerns, these etching primers are not considered do-it-yourself friendly (although they were used that way for years).