Don't flame me, but..........

[beedees]

is there any rattle-can primer that will work O.K. under s.s. urethane paint? Doing a fast and nasty on son's p.u.. (one fender)

[JR]

Nope. I've gotten away with some good spray can self etching primer for cut thrus around edges and stuff, but I assume your not going to the metal.

If there arent any dents your fixing you can scuff the whole fender with 400 grit and paint directly over the original paint. It won't need a primer if the factory e coat or primer is already there.

If its a new fender you can just scuff the ecoat with 400-600 grit and paint directly over that. If you repaired a dent or flaking paint, you need high build primer.

Omni makes a cheap version of PPG K36 which works just as good an is a whole lot cheaper.  I'm assuming your using base/clear paint here.

Hope this helps!

[Mike DC]

 
I wonder if Omni's primer would work equally well under anybody's else's urethane topcoat (DuPont, PPG, Sikkens, etc).

Anybody know?

[Silver R/T]

It should, even though if paint does fail they won't warranty is since you used someone else's topcoat.