I use a soap designed for cars that won't strip wax. I typically buy the best price qualifying product at walmart. There are a lot of places in the US where the minerals are so high in the water that washing with tap water spots your coach to the point of having to strip it down with vinegar and start over so be sure you aren't washing with bad water.
I use Wash Wax All
after washing or instead of using the local bad water.
Practical Sailor did a recent test and Turtle Waxs Ice Premium Care, with Sudbury Miracle Coat and NuFinish Rapid Shine were the top performers. They did not test wash wax all.
I am currently trying out Meguiar's Marine Paste Wax
on the roof to see how long it prevents oxidation.
I have been using Meguiar's G18220 Ultimate Liquid Wax, 20 oz
on the roof and sidewalls. It has prevented oxidation on the roof for about 6 months but it stops beading after 3 months. I am hoping the paste wax does better. The Ultimate Liquid beads on the sidewalls for a year but the Wash Wax All probably helps.
2013 Winnebago Journey 36M DP. Full time since 2015. 1987 FJ60 Flat Towed, FAILING 2000W of GRAPE Solar
, 800AH LifeBlue
LiFePO4 batteries (excellent), SMI Toad Brakes.