I'm painting a dual snorkel hood scoop for my demon. It's new, and fiberglass, of course. I sanded it, then washed it in hot, soapy water and rinsed and dried well. I applied rattle can satin black paint, and it adhered well. But there were a few low sand marks, so after a week, I sanded it, washed it, and applied primer. The primer immediately wrinkled up. I've repeated the process a couple of times, but the primer always wrinkles up. What's going on here?

its reacting to the black paint, u most strip to bare fiberglass and start over.

Sounds like you've got a compatibility problem. If the black paint you're using sands nicely, why not just add another coat or two? After it dries well sand that smooth and you're good to go ya?
An alternative would be to find another kind of primer which goes on without reaction problems.

Thanks for the replies. I'll try sanding and applying multiple coats of the satin paint, skipping any future primer.

stop using cheap rattle can paint, that is your problem, the solvents in primer eating up the crappy spray paint,strip it all off,apply few coats of sealer/primer,followed by few coats of automotive grade paint that won't fade in couple of months

you can use enamel over lacquer but not lacquer over enamel