Clear Coat Over Exterior Paint

I have painted my teardrop and now a couple people have told me I should put a clear coat over it to protect the paint job. I went to The Home Depot and asked them and the only thing the guy showed me was a can of stuff to put on wood. I asked if I could use it over paint and we said he thought so. I turned the can around the the directions and it said "Remove all paint."
So I put it back and decided to ask you guys.
Do you have a clear coat over your paint? If you do/don't do you have a suggestion of what to get and where to get it? About how much is it?
Thanks!
Dianne
Here is the outside...


Do you have a clear coat over your paint? If you do/don't do you have a suggestion of what to get and where to get it? About how much is it?
Thanks!

Dianne
Here is the outside...