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If the base coat is metallic, you may never get quite a perfect match without respraying the entire area, blending it in at a body seam or contour.
Applying the clear coat, you are going to need to scuff sand the existing clear and the paint a little, in order to get the new clearcoat to "bite" and hold on long term, as well as blend in (while it is clear, it will have an edge to it if you don't feather it and blend outward with the clear)
What grade of sandpaper should I use to scuff it? 400? After it is dry should I give it a second coat or leave well enough alone if it looks ok?
400 is good, enough to "rough" it but not appear scratchy. If you get runs in the clear coat, when it is fully cured (wait a couple weeks to fully cure, even if it is "dry" after a few hours) you can wet sand it to remove runs with(###) ###-####grit wet sanding paper. Use a hard rubber block to maintain a flat surface with the paper so you don't scratch or burn through.
A second coat is always better, but if you do that I might even suggest blending this coat all the way to the edges of the roof, to even i all out and reinforce what you have (since your roof seems to be a wear area, you must be in a sandy area)
Not sandy area. Colorado. HOT sun all the time. I am surprised it lasted this long without fading. Thanks a heap for your expert advice. 5 stars coming your way.
Yeah, I lived in Texas and saw a lot of that. Good luck on the paint, and do it where you won't get dust in the clear coat.