Hi, Tim-

Congrats on your progress. We'd love pics, if possible. You must have some serious bend and twist in those strips.

In my experience, most of the material is taken off (during fairing) by the plane and scraper. I wouldn't sweat the sanding too much, just try to be conscious of your thin spots and treat accordingly.

Also, it is not too much of a big deal is some more gaps come out after your first rough grit. Just fill again, and continue with the next grit. The finer grits do not take off much at all, so you probably won't have any more gaps appear. Good luck! Mike