I used bars keeper friend to remove lots of oxidation. Then follow with a good wax. It worked pretty good. You will never get that full shine again. You will still have to keep doing this year after year unless you wax it every 3 months or so. Mine is 12 years old and one side always in the sun it fights me every year. The other side is always shaded and still has all its graphics but had to remove all faded and cracked graphics from front driver side and rear and fight oxidation all the time.
2002 F-350 Crew-Cab Dually
V-10-4.30 gears Mag-Hytec diff.cover
w/Amsoil-6.0 trans cooler Curt Q5 20K hitch & bedsaver
2005 Keystone Challenger 34TBH-Fifth Airbourn