I painted our wall speakers the same time I painted the room. What I did was use a roller and roll almost ALL the paint off the roller onto the wall - to the point where almost no paint is coming off the roller at all. Then I laid out the speaker grills on some newspaper and gave them a couple of coats with the near-empty roller. Worked like a charm. I let them dry for a few hours and they matched the walls perfectly. For the trim rings on the speakers themselves, I just used a small paintbrush, also with almost no paint left on it. For me, one of the biggest benefits of in-wall speakers is getting to paint the grills to match!