Ideally I'd have flipped the trailer over and done some grinding on the bottom side, and had the expanded metal tailgate sandblasted, but time and budget ruled that out.
I used an industrial enamel from NAPA stores, sold under the Martin Senour brand in a dark machinery grey color. The first coat was sprayed late on a Sunday afternoon, and before the paint dried the temp dropped from 65* to about 50* and heavy dew settled. The next day I came home from work and looked at it, the paint had dried totally flat. So the next Saturday here on the west side of Savannah we had unseasonably warm temps for early December. 76*, and I sprayed on a second coat. This came out nice and shiny.
I also welded up some guards from 1/8" flat steel to keep the tail lights (hopefully) from getting broken off. I then installed new LED tail lights. The kit was about 25 bucks from Harbor Frieght tools, I didn't keep really close records. I however did not use the cheesy "scotch lok" wire connectors, they pierce the wire and don't seal it. I used butt connectors and shrink wrapped 'em.
Yes, that is a shitty weld on the top of the guard. I know. My Hobart 135 MIG machine was giving me fits, and it normally about welds itself. I'd strike an arc, the arc would cut out, and back in, like a machine gun. I later found the problem- the small leads from the trigger contact go through the main cable with the liner and wire for the feed, then come out in a small loop right outside the body of the machine. In my moving the machine around or putting things down on the bench it sits on, the small leads had gotten nearly cut through. So each time I struck an arc, the amperage would build (it was only contacting on one or two strands) and then it would loose the connection, and effectively cut off the weld.
All fixed now. Here it is with the new lights on. Still to do are some longer, heavier saftey chains, and put some plywood on the sides. Oh, and fill out the form and get it registered! Until then, I'll hang my boat trailer tag on it if I need to use it.
Here's a couple "befores!"