I need a VERY small amount of DTM high build primer for a repair on a gas tank. I am also needing a small amount of high build primer to smooth out some fiberglass saddlebags. Can I use the same DTM high build primer over sanded gelcoat, fiberglass where the gelcoat has been sanded through, or over epoxy primer? Do you have any suggestions of what DTM primer to use?

I would say yes as long as you sand the panel. We use Dtm primer on everything because of ha sing metal and plastic when we repair cars.

You guys should consider the Tamco DTM HP-5310 primer. I have restoration shops in my town using it now and dozens of others out there ordering restock on a regular basis.

It's actually bizarre how good this primer is and I'd never believe it unless I was using it myself.

You'd be surprised how much you use this stuff once you have it. It'll go over any automotive surface (plastic, metal, etc.) and you'll end up using it around the house or shop on other projects. I just put a new commercial steel door in my walkout basement and primed it with HP-5310. Sprayed Sherwin Williams latex enamel over it; came out awesome.