I have some serious scuffing on my car’s door sill. I bought some black xpel film to prevent this in the future, but I want to do something to prevent rust from forming underneath the film.
I bought some color matched touch up paint, but I’m wondering if I need to remove all of the paint and primer from the area. Since I don’t care how it’ll look under the film, I’d like to just rough it up with sandpaper, prime and paint it, and then slap the film on it.
The part I’m worried about is that it’s a fairly large and irregular scuffed area. Some bits are down to metal, some down to primer, and some still has the clearcoat. I can’t really mask it off and only get primer on bare metal and the original primer.
The reason I don’t want to sand it all down is that it’s a difficult area to sand. I’m worried I’ll fuck up the paint beyond the area that would be covered by the film.
Can I do it the lazy way, or should I just bite the bullet and sand down to metal?
It’s water based touch up paint if that matters.
The knowledge I have is from researching this stuff for bikes and it has a lot of overlap because we use the same materials and supplies - e.g. 2k rattle cans and clear coat. So I’ve read a bunch of recommendations and videos about cars as well.
Most car people will say that if you want to prime+paint+clear coat you need to take off and redo the whole panel. Like sand it down to at least the primer and go from there for the whole panel. This also usually involves proper color matching, knowing the exact color code. Basically nothing adheres well to an intact clear coat, including primer, so the edges of any “spot fix” with your strategy will be prone to flaking, as the clear coat will be intact at the edges. Some people seem to get away with spot fixes using these supplies but they also tend to be experienced at doing these kinds of things, have airbrush setups, that kind of thing.
If it is a small section, many people use best-guess color matched nail polish as a spot fix.