Bought a rust free trailer that was never used and just sat outside. First step was to strip everything and cut off brackets to replace with adjustable ones to fit my boat correctly. Replacing everything. lights, wiring, bunks, wheels, brakes, brake lines, leafs, all hardware, A-60 tongue etc...
So far I have 35-45 hrs into it to strip, grind any rust spots, sand entire trailer, prime and line with 2 coats. Here is what I did and figure this info will be helpful to anyone thinking about it. I used the $10 HF HVLP gun and sprayed epoxy primer with the stock 1.4 tip. Then drilled to 2MM to spray the liner. GET A RESPIRATOR!!! You cannot do this job without one. Even a dust mask will not stop all the sanding dust and is needed for clean and paint. It's nasty and you will be covered.
Strip and washed with soap/water
Sanded with 120 Grit on a DA and by hand in hard to reach areas
Ground to bare metal where stickers or surface rust spots were with a wire wheel
Drilled cross bar holes larger to help with water drainage
Wiped trailer 2 times with Acetone and 20 microfiber towels
2L of UPOL Epoxy Primer 3:1 with 1.4MM tip 45psi
waited 1.5hrs with 85 degree temps
7l of raptor liner with 2mm tip doing 2 coats and waiting 1hr between coats. 35-45psi
Treated cross bars with fluid film