Like he said!!!

DO NOT BE WORRIED ABOUT TAKING YOUR TIME!!!

I can easily spend 3-4 hours cutting a cowl.

BTW: I hold the intake of a shop vacuum tube between my knees angled at the cowl I am working on.

This keeps the fiberglass dust out of the air, though wearing an air mask is a good idea.

If you are cutting a large area out, you can also use a drywall side cutting bit in a dremel to help carve out large areas.

The side cutting bit chops through the fiberglass like butter, so you have to be very careful. You should not use a side cutting bit for your final cuts though... do this as suggested above with a sanding "drum" not a disk.

The sanding drums are round cylindrical bits of sandpaper over a cardboard structure...

Dremel has two sizes, the normally available larger .6" diameter size and the sometimes hard to find .25" size.

The latter is great for cutting out bolt holes and holes for High Speed Needles, etc.