I painted the inner fenders on my 70 Chevelle with por 15 (I did not want them to ever rust), it is the glossy black, I want the finish to be more of a satin. I was wondering if I could spray SEMS (in a rattle can) over the top of it? At the time I was not aware that por 15 had a chassis black that probably would have looked better than the gloss that I used. Thanks again for the help.

You can scuff the POR-15 and the spray the sem's should work ok I did the same thing on my 64.

FYI they say to prime POR-15 before it has fully dried, otherwise there might be adhesion issues if you try it later.

Thanks for the tips

POR15 also makes 'tie primer' for doing exactly what you want to, after the POR15 has cured.