My RV is now 15 years old and I bought it used 9 years ago. For the first several years, I washed and then used various car/boat wax products. It seemed to be an endless and frequent process. In addition to accumulation of dirt, black streaks were an issue and seemed to start again very soon after washing and waxing.
Three years ago I switched to Zep and have been extremely pleased with the results. The first application will require a lot of work. I washed with soaps and ammonia solutions to remove all traces of old waxes and finish. I then removed the oxidation by slowing rubbing with Bar Keepers Friend and a Scotch pad. After that application of the Zep finish was easy. I just use a small rag dampened in finish and lightly wipe it on. With a light application there should be no runs, drips or issues but it will take at least two light coats to achieve an attractive shine. I used 4 applications. The finish shed dirt and absolutely no streaks occurred for the first year. In fact I did not even have to wash the RV with soap. I just sprayed off the dirt. At the end of a year, it looked just as it did after Zep application. I did wipe on another thin coat. The next year I wiped on another thin coat. I will do the same this year after the Winter months. The Zep finish protects the finish from oxidation. I do understand that Zep does not include a UV protectant but that does not seem to be needed. If that is a concern, I understand the RV can be wiped down with Aerospace 303 and then Zep can be applied with no issues.