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I took about 4 coats of old paint after stripping the paint w/aircraft paint stripper. Now I have a red primer? under bare metal and then covered w/a gray tough primer hard to remove. I used 36 grit to sand, now I am going to 120 grit, going to bare metal.
Am I ok, or I still need to go down like 220 grit before I put the etch primer?
I am planning PPG etch primer with a respirator, since the last time I sprayed this etch primer with a small mask primer, my lungs felt weird, and it was only a 5 foot panel. Then I will apply a small coat of epoxy primer before going to the painter.
Am I doing the right thing? Need advise, any imput will be appreciated. Thanks in advance, Jose

I usually sand a panel to bare metal with 80 grit d/a after using aircraft stripper. Then apply my etching primer, wetsand with 320 grit, ( just to rough it up) then apply your urethane or epoxy primer.

You'll be fine even over 40 or 60 grit-paper-sanding marks, don't worry about that

Thanks guys. I will re-sand and clean the bare metal tomorrow and then apply that nasty PPG etch primer.

The more grind marks you put in the metal the more primer surfacer you will waste unless you are using epoxy primer for the first coat. I use a sripping pad with 80 grit at low rpm to get to the original primer followed by 120 or 150.