:here is a quick answer that might be useful, until someone with more experince responds...

I had some crummy edges, selvege edges on tape reinforcement layers on the keel, overlapping layers of fiberglass on the bow area, etc. I just applied the fill coats over them ... then when I sanded, the rough edges got sanded away. If an overlapped area is really rough, I guess I would recommended scraping it with a carbide-bladed scraper before sanding.

"2nd and 3rd layer..." Are these layers of tape, or layers of glass?? What weight? Everything I mentioned applied to one layer of 6 oz. glass, with either one or two more layers of 6 oz tape on the keel and hard chines.