There is no way to prevent rusted nail heads from bleeding through paint. To treat the surface won't stop the rust on the underneath side. The best way to have a great paint job is to remove all the rusted nail heads and replace with stainless nails or screws. The only way to remove the nail...
Good thought, I could just use the nail head gone drill bit and then run a stainless screw or nail in next to the removed nail head......I would be concerned that the rusted nail head is also rusted underneath. Thanks for your comments.