I tried the Totally Awesome on my enclosed car trailer, it caused some awful streaks but removed the crud. I had to quit immediately and was not able to undo the damage. Don't use it without first testing a small area, that stuff can remove paint and all. I then did the entire trailer with Nu Finish and that took considerable work and still didn't clean well. Nu Finish is best used on a new trailer and never allow it to completely deplete.