If the fiberglass has got wax on it already, I would recommend this easy to use finishing product
However - this is no substitute for completely worn off or missing wax. You can get wax that goes on easy - like this one
You mention that you are going to wax followed by a rinse with water. This is not the way to do it normally. What you do is that you clean your RV with soap and water. Then you apply the wax or the finishing product, and this is just buffed with a clean cloth. So no water after waxing/finishing.
Wax on - wax off