When I am installing aftermarket parts, I agonize over drilling holes in my car.  This is especially true when drill shavings are going on the carpet, like when working under the dash, or anywhere for that matter.  Anyway, I remembered I had a pan from an old Super Turbine 400.  I stole the doughnut shaped magnet from the pan and positioned it over the holes as I drilled them. A bit of saran wrap around the magnet would help in removal of the metal particles.  Or, it would keep the doughnut fresh until the next time!