What to use to prevent UV fading/paint oxidation?

[4RXLA]

My trailer was painted silver with pewter trim about 20 years ago at Inland RV and the original blue vinyl stripe was also removed and the aluminum painted blue. The trailer has been under cover and the paint has held up beautifully except in a couple of spots on the curbside just forward of the entry door where years of daily sun and overspray from a shrub sprinkler have caused the silver paint to develop some white blemishes directly under the blue stripe moulding and the blue stripe itself has faded/oxidized. Also, the pewter paint on the rear bumber has faded from the afternoon sun. A couple weeks ago I bought special cleaner wax and removed the oxidation from the blue stripe and restored the color. It has a liberal coating of NuFinish on it currently as with the rest of the trailer. Even the rear bumper color came back better than I expected. I'm wondering if there is a special product I can buy that will better protect these painted surfaces from further fading/oxidation? As for the white blemishes on the silver paint, the cleaner wax caused most of the blemishes to peel off...white flakes that look like a clearcoat. There is silver paint underneath. I would want to protect this area and rear bumper in a similar fashion as the blue stripe. I wanted to get the areas repainted at Inland but Andy told me that it can't be done with quality paint anymore in California due to environmental regulations and the extremely high cost of the paint. The trailer continues to be stored indoors but there are skylights in the building that allow the sun to shine directly on the trailer. I want to make sure I have maximum UV protection.