Help in how to handle the "corrugated" sides of a 5th wheel

Instead of the flat gel coat type side this 5th wheel has the aluminum mini corrugated type sides and my real issue is how to you get the oxidation off and any protection on without just loading up where 2 panels hook together as it seems to make the perfect spot for and product to build up and have to be cleaned by hand to get it out.

Does this make any sense to anyone, and do you have any tips for me. I will be doing this with a XP and have Flat and CCS pads but wonder what would work better or if I need to buy something just for this kind of job.

Need a picture. I have worked on semi, but have no idea what your talking about. Sorry.