I can't add much to what Scott said. I mostly scrape in cases like this. The only problem with sanding is that you need to let the epoxy set up hard so it won't gum. It may appear to be sanding ok, but you might notice little white spots appearing in the weave. This is because the sanded gummy epoxy is depositing in the depressions. You can check this out by picking the little white spots out with a knife. This is a bear to do if you have 10,000 little white spots. When the epoxy is hard I don't have any trouble in spot sanding...rather than doing the whole boat. I just check with water to make sure the transitions are invisible.