shaving a dash.

ok after i finish my bodydrop, andbefor i put my interior together, I wanna shave my dash clean. Kind of like the blue and white mazda from this months mini magazine. How do i go about filling all the holes for ac vents and shit. can I fiberglass them or what,. I was told that fiberglass wont stick to plastic. is this true and how would i go about doing this to my dash?