I reorganized the trailer tongue this spring so after stripping as many parts away as was practical I just wired brushed it and spray painted it with gloss black Tremclad. I actually found it quite easy to control the spray pattern and only masked off critical areas such as diamond plate on the front wall, the key being to use less paint rather than more and if necessary do a second coat for a proper finish. It may not be a factory finish but it does look pretty good for the little effort it took. Our trailer has an open underbelly, making access to the frame quite easy so that'll be next. :)