I have been using Collinite Wax #845 Insulator wax on all of my vehicles, RV's, enclosed car trailer, etc. for over 20 years and have not found any wax that is easier to apply and remove. I wax my T.S. MH twice a year and it still looks like the day I took delivery. I can wax my MH with less than half of the bottle (pt.) and still wax several of my other vehicles. I have used it on all of my classic cars that have very expensive paint jobs, as it does not leave any swirl marks and is easy to remove with a cotton towel.
I also recommend their #840 Pre-Wax Cleaner that works great to remove road dirt, etc. if you have not waxed it in the past. Some Marine Stores sell it or you can order it direct from the company.
http://www.collinite.com/automotive-wax/ Any good car wash soap would work well. Spray just enough water to get it wet and then wash is with a sponge or car wash brush, before it dry's rinse it off, it does not take much water, for a small trailer.