Realistically you have to keep coating anything as the UV breaks down the inhibitors over time. Epoxy really hates UV 
The chemist here at work was saying titanium dioxide? I guess it can be added to resins for UV protection. WOuld be good for infusion. Again the prepregs are starting to go that route as well, which is great for us lovers of naked carbon.
So what car wax are you using? I should probably get something like that at some point.