Wax or no wax
I too use the 303 works great, use it on the roof also, 303 is also great for the rubber gaskets on the slide outs.
I also use Scrubbing Bubbles foaming shower cleaner to clean the bugs off the front of the trailer and my truck bumper and bug deflector. Just spray let it foam and rinse it off. My wife said it cleans the fiberglass shower, so the RV is fiberglass, works great. Sam's club has a good deal on 3 cans. Can't find a great deal on 303, but it is worth the price