I have been taking the frame to bare metal on my 60 f100. I have done the whole rear suspension in krylon rust tough gloss black enamel. It came out pretty good, not for show quality of course but nice. I had used.por15 on the frame before but doesn't work well with a clean frame. So I plan to use the krylon on the frame aswell. Should I use just regular krylin primer first or etching primer?