I'm in a quandary. I have been patching filling rust on a Pontiac Sunbird...did a pretty good job to my eye anyway but I am getting mixed signals on prepping the original paint areas versus those with filler.
I called the company that manufactures the basecoat and reducer I will be using. The company guy said to lightly sand the original paint with 600 grit sandpaper, clean off the dust and just apply the basecoat with my spray gun in several coats. I asked him "What about sealer?" and he said not necessary.
However on the Internet several sites have guys saying NO NO NO---put down sealer before basecoat. So if I put down sealer before applying basecoat will that not reduce the adhesion that is provided by my sanding the original paint? Or should I put down the sealer, THEN sand?

The areas that I patched and filled with filler have been primed with high build primer, sanded and I am guessing just treating those areas the same as the original paint areas is OK, probably give them two or three pre-coats of basecoat. I'm brand new at this so if I am wrong and made some stupid statements here I am open to the wisdom if this austere group.

First: Primer
Second: Base coat
Third: Clear coat

Voila'!

While we're here: Thank you for keeping a Pontiac Sunbird going! I didn't know any were left in the world!

This is the first one I've heard of in probably two decades that is getting painted.

Thanks (as always) for weighing-in, Cathedral Cub! Yes, I've been having a ball with this project. There was SO MUCH to be done to
remove terrible rust. I loved this project so much that I am actually anxious to finish it and start my next one on my '86 Buick Regal.
The nice thing about this car is it'* small and as this is my first attempt at something like this, it made it a good learning platform.

Are you not a proponent of laying down any sealer on the original paint prior to basecoat?

When I'm done I'll post before and after pics...I am going to be like a proud parent with a wallet full of photos.

Cool!

I'm not necessarily for or against a sealer. I just know that in just about all cases, primer then basecoat then clear coat works well for a long time.

If you are painting any bare metal it bust be etched with etching primer. All other surfaces can be primer, color and clear.

Thanks carfixer007. I did use etching primer on the bare areas. Is primer necessary on the areas that are just original paint that I am just wanting to overspray?

No.So long as you don't sand through the existing primer coast you'll be good.

sounds like youve done your homework. trust your instincts, you'll do great.