Not sure about the manf. recommendations, probably in my trailer's manual.
But, I use Mr Clean magic erasers. Work super fast and easy. I also hit it with a bit of windex now and then.
Follow up with a nice coat of carnuba wax and it lasts all season with just a light car soap and water wash.
That's the sides only, not the roof.
2011 Flagstaff Classic Superlight 831RLBSS "Atrium slide"
Husky Centerline Hitch
2016 Ford F-150 EcoBoost SuperCrew, Lariat Sport, Max Tow package