Clean it first, but most importantly, dry it, and everything around it. If water accumulates near the grill, it could drip down while you are spraying. This happened in a few places for me an it left a little mark, but it mostly went away after a few more coats. Blue 3M tape is pretty good too for protecting the lights and vents.
Remember to leave a slight gap when masking, you do not want to tape right on the line.