Apply a heavy tape in the area you are going to drill and drill several small holes in the area in which you wish to drill the larger one. Go slow ith all drilling.
use clay or plumbers putty and create a little volcano opening around the place where you want to drill the hole. Put oil in this pocket you create. Then starting with a small sharp drill bit do a pilot hole, followed by the larger hole that you want. The oil will prevent the drill from overheating and help prevent the coating from chipping as it gets hot.