I've used the Black Satin twice now. Works great. You CAN brush it on, but I suggest spraying it like I did the second time. It'* far more effective than powder coating. The small can will be enough, and you don't have to thin it.
If you don't have the equipment, you can use the little glass jar and propellant can (touch-up sprayer) from Lowe'* or Home Depot. Most paint stores should also carry it. Don't do the inside. Just the outside. And remove it from the flanges (or mask before which is a better idea) before installing them. This stuff is VERY difficult to remove once it'* heat bonded. I baked mine ahead of time so they wouldn't scratch when I installed them.
In spite of my abuse, they have held up VERY well.