I washed mine down this weekend and used the 303 over the whole thing for the first time. Last year I used nufinish on everything but the decals and 303 on just the decals.
This way was much easier. I applied by hand with a spray bottle and microfiber cloth. Still took me all day and still kicked my butt! LOL
Decals still look as good as when we picked up the trailer last year.
I was unaware about using it on the roof. Seems like a good idea though. Not sure I can get to it until the end of the season though, but the roof looked same as last year as well.