It took a while for me to locate these photos, but this was my "crowing achievement" painting the plastic or vinyl items on my previous campers. This was our Outback TT, before and after paint those vinyl propane tanks. I did a lot of detail work on that camper after 5 years of sun dried fade:
This is a photo of the camper when it was still fairly new. The propane tank cover had not faded yet. It faded a dingy grey. It looked very similar to the electric jack cover.
You can see the difference in how much that plastic faded over those years by looking at the difference in the jack cover:
And here is the same tank cover after using the black Rust-o-lium (Professional) spray paint (2 coats):
I have also quit messing around trying to wax and protect metal parts, like the trailer frame, stuff like that. I just spray paint and never have to wax. I would not do that on the side of the camper, but it works VERY well on metal and plastics!