Hi Manyo,
Your question was - when blocking is complete, can I just nail it with more hi build , or do I need to reapply epoxy sealer and then primer? I did violate the epoxy and there are a few small areas of bare steel showing.
Paul's link above offers excellent advice and mostly covers it. But in regards your specific question about spraying more coats of 2Pak primer filler or Hi Build over the small exposed bare steel areas that you rubbed through, my advice would be to look up the data useage sheets for PPG or better, contact the tech department and get specific advice from them. I'm assuming you're using PPG brand all the way through. Why i say that is because paint do's and dont's can vary from paint company to paint company.The key question here is whether you can spray epoxy primer over 2pak primer filler, when it comes to spot priming your bare metal rub throughs. Or to put it more directly, can epoxy primer be successfully sprayed over 2Pak primer filler, because in your case, that's what you will end up doing if you attempt to spot prime again with epoxy primer over the bare steel rub through areas. I would say no to that, but i may stand corrected by different paint companies, and spraypainters.
For example, some painters might say spray a light coat of single pak etch primer on the bare metal areas, and then move into your 2Pak primer filler to build up again, and some might say just use the primer filler straight onto the bare steel rub throughs. So to be sure you get it right and nail it, i would talk to the boys at PPG and get the exact lowdown on what you can or cannot do in this specific instance.
Hope that helps,
Greg.
Handy hint - dust a light coat of single pack primer over the steel areas to temp seal them. Later you can wash the primer off with thinners and then continue to do what you want to do. That process will stop any rust from growing.
