Ouestions 2-oxidation&clear coat

[Sharon Lee]

I just remembered another question.
The previous owner took scotchbrite to a portion of the top of the trailer
(someone should hang him for it) It's a spot about 1 foot long and a half a foot wide. How could I get rid of it? Do I need to guess what grit he used and work up from there? What grit is the finish? I also noticed a good amount of oxidation near the roof. Would regular lacquer thinner work to remove the coating? It's a plastic coat isn't it? What is the replacement for the clear coat that you recommend? Is it something that comes in a spray can or could you use a spray gun to apply?
Once you have it removed what do you recommend to polish it?
And what happens if you just leave the oxidized spots alone??
Thanks again- Sharon Lee