To cut the holes I use a dremel with a carbide bit. I use an 110vAc dremel as I don't think the battery powered ones I've had turn up fast enough. The faster these things turn the less likely they will grab and make that big huge hole I'm sure many of us have done before. I use the dremel to rough out the holes then a selection of Perma-Grit tools to finish them. This makes for nicely finished work keeping things looking neat.
I started with the intake holes. I first cut away the tape on the marked lines. Then grind out the holes with the dremel and use the perma-grit tools for the finish. I then take some 400 or 320 sandpaper and give the edges a light sanding.
Now 16 more holes to go!