You can always try painting with some kind of light duty acrylic or even enamel paint, and then sealing the whole thing in a nice, reasonably thick layer of clear epoxy. Sealing the part with silicon would be perfect as well, as long as you make sure the silicon can bond with the painted surface (not sure, myself). Otherwise, paint wont work where animals will eventually live; even non toxic stuff is a no-no (even the regulation-spec stuff in the shop makes me want to lie down and choke to death, so I just hold my breath...).
Other than that, Im still not quite sure what it is youre trying to paint again...?