To drill fiberglass, I just use available drills and mask the area. Put the tape on first and transfer the marks from the template. I use a center punch also, but I do not hit it too hard. I use hole saws for holes 5" or less and a jig saw for larger holes. I use an angle grinder with a 4.5" grinding disk for metal to do all the trimming and edge grinding.
Tape the gel coat side and forget the inside, just go slow as you break through allowing the hole saw to cut. What you are trying to prevent by masking is that the saw will grab a glass fiber and yank it hard enough to break off a chip of gel coat. To debur, I use files, half round or more often rat tails. Bevel the edge bearing down only one way when the gel coat is supported by the underlying glass. Debur the under-side but make sure you angle away from the gel coat. When you are trying to locate a hole accurately that you cannot mark with a template, if the hole is big enough, drill a smaller hole and mount the part and peer through the small hole and see how close you are. Mark it and use a round file to enlarge the hole in the direction you need to go. The hand work is slow, but a lot faster than doing metal.
I do most of this outside, for obvious reasons, and I use a fan to blow all the little particles away.
David
