I see the sense in that, but the grit is more likely to come off that way than if you used the self adhesive stips of sandpaper some rod building supply houses sell for that purpose. To that end, I think it would be wise to use an air compressor to blow out the grip and follow that up with a quick swipe with the rat tail file to knock any other grit loose then blow it out again.

As for the original question on repairing scratches, you should be able to repair some of those by lightly buffing the area and then putting a decorative wrap down with thread work or a feather inlay or some other kind of decoration that gives a "reason" to cover the area with an epoxy rod finish. If the scratch is on the "side" of the blank, put a feather inlay on it and one on the other side to balance things. Cover it with thread work, but repeat the thread work as necessary on other sections to make it all look like part of the "plan."

Some of my best pieces of leather work or wood carvings evolved from needing to cover a mistake. Of course I royally messed some stuff up trying to "fix" it, too, but you can usually come up with a nice way to hide it.