Needs to have some kind of UV blocker to have a chance at all.
U-pol clear spray paint from amazon is the best I’ve used. The buffing and polishing as described earlier, then a solid cleaning, then 2 coats. It lays down differently that rust oleum or krylon, so practicing first on something else is highly recommended. It lasts years and will barely yellow, until the plastic beneath it simply comes apart. I’ve done this to many, many, vehicles - my own, and probably well over a dozen for folks who need help whom we look after at my church.
it was a bitoger 10+ years ago who recommended the product and method to me!