How many layers of fiberglass cloth you use depends on how thick your fiberglass shell is. Since I was trying to repair a 1/8" wall, I thought 3 layers of fiberglass material would be appropriate.
A sailor friend of mine informed me that I would need to glass in a large patch first, and sequentially step down to a patch the size of the hole. I used kid scissors that I didn't particularly care about to cut the patches.
The largest patch extended a little past the outlined perimeter, with the next two patches cut sequentially smaller.