Powder will cover some pitting but not all, if it is deeper than 1mm it is going to need filler to be smooth.
Just my .02, but hey, it is a trailer, I'd just paint it!
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Drew F.
Rising Sun 4x4 Club
76 FJ40, 85 fj60 Engine and Ignition, 35" MTR's, Warn 8074, 4" of lift TPI, snorkeled, racked, Mini-truck P/S... and sometimes running.
Friends don't let friends drive Thornbirds...
My camping trailer build up thread.