I used RUSTOLEUM, flat black paint. It came in a half pint container for less then five bucks.
I also used a 'weenie' roller, or 'cigar' roller. They look like thier names.
The paint is oil based, but with that roller, I did not need to mask off anything, just rolled all the way to and over the trim on the back side.
It took three coats, but it dried, within a half hour each coat, the directions said something different, but I just went ahead, and in hour and half was done.
The paint will last long time, and actually will come off with a sharp razor blade, should you change your mind in the future...
When I was done, I just through away the roller, and did not have to clean anything up...
Bill