Factory paint? Sand smooth with 180 dry (with a DA & by hand), for the best adhesion prime with PPG DP epoxy primer. If the surface is smooth before priming, you don't have to sand the epoxy - just start shooting the paint after a 30 minute wait for the primer to tack. If it's not perfect (or if you want a really smooth surface), you can sand the epoxy with 400 wet before painting, but you have to let it dry a day or two before sanding 'cause it's very sticky.
Any repairs may need a hi-build 2K type primer over the epoxy in order to block them out, them prime those spots with epoxy again.
"Adhesion promoters" are crap.
If it's been painted before, you should strip off all the non-factory paint, either by sanding or stripper.
http://gafieroclub.org/bbs/index.php?topic=469.0http://gafieroclub.org/strip_fiero.shtmlHTH,
~ Paul
aka "Tha Driver"
Custom Fiberglass Parts[This message has been edited by Tha Driver (edited 01-13-2019).]