IIRC the WeatherGard boxes are clear coated. Depending on the age you might have to strip them to get them polished back up. I had a full set on my 1997 F-150 work truck, that came off of an older truck. Danged company sold them with the truck in 2006... I wanted them boxes!
As far as polishing you will need a soft flap wheel, looks like it is made out of a bunch of mop strings. It will still get eaten up, just not as fast.
Aaron
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