Enamel, lacquer, urethane? Which paint?

[Grounded63]

The JP 202 you referenced above. Can not be sprayed over bare metal.

For something minor like the break through to bare steel. On the interior bodywork you are describing. You can probably just use some rattle can self etch. PPG & SEM both have it available. It wouldn't really be my first choice, but should be perfectly acceptable. You have to limit its over spray on to body filler. Any excessive over spray/coverage on top of polyester resin products. Should be sanded/scuffed back, once the self etch has flashed/dried.

At one of the production shops I worked at. If there was minor break throughs to bare metal. In e coat or bodywork just prior to sealing. We would spray those small areas with rattle can self etch.

I wouldn't want to spray an entire bare metal fender down with it. But, it's to bridge the gap, between a minor amount of freshly exposed metal during prep. And the application of a non direct to metal product, that can go over a self etch product.