Long story short, I had a new PJ (Dunlap) trailer stolen, beat to piss, etc. I was able to recover it and a couple years later I finally got time to restore it to better than new condition. I used a duraliner product and hit all the steel with it. It is now just like if you Rhino lined a truck bed. Solid as hell, don't scratch.
Here is a pic after I got it done with the new fenders mounted.. Cost me around 80.00 and about 3 hrs of my labor to re-finish it..
I thought POR 15 wasn't sunlight resistant, I'm pretty you have to top coat that stuff, that meens painting it twice.
I would just use Rust-O-Leum, it works like a champ and is way cheaper, you can get a gallon of Rust-O-Leum for what a quart of POR 15 costs. Get you a nice thin nap roller and a good brush and it'll look great, the paint will flow right out nice and smooth and hold up great.