coltcarbine,
What a find...Dads are great. I usually do a project in this order. Inspect the trailer for broken welds etc and get it back together structurally.
If you are going to sandblast it, do that now and get some good primer on it.
After all the sand and dust has settled, do your mechanical...bearings and brakes.
Now you can paint the trailer without fear of greasy fingerprints.
Finish it off with wires and lights and maybe new rims and tires.
Get ready to have friends borrow your new, pretty trailer!
Stuart