For fiberglass and gel coats believe it or not ZEP Wet-Look Floor Polish is the best. I wouldn't use it on metal surfaces but it's ok for plastic as well. You wash the fiberglass first with regular to prep the surface, let it dry and then use a damp but very wrung microfiber towel or spung to apply the polish to the surface of the RV, boat or what ever fiberglass thing you want polished. You'll need to do about three to four coats five or so minutes apart or until the last coat is dry. Use a 5 gallon bucket with water to wring out the microfiber cloth before you add more wax to the towel/sponge because it'll turn your driveway blue when it dries if you let get all over the place. I don't know why it just does.
There's videos all over youtube of other people polishing their RVs with Zep. Here's one here: