On one of my projects, I used POR-15, and there are a couple areas where it didn't cover. it ran away. small areas, mostly fish-eye type spots, some bigger. I guess I didn't get it completely clean in some of the hard-to-reach areas. Can I just use like a pencil spot sander and some cleaner on the naked spots and be ok, or do I have to grind away a larger area around it?