It is better if you sprayed some SEM etching primer on the bare metal spots, then paint over the etching primer with your black paint-make sure you paint it with in the window period for the SEM etching primer.If you wish you can also just use some spray can sandable primer on it, because it is inside you car and sand smooth when dry and then paint.
As far as the correct black, I would use a satin black, or a low gloss...They also make a Bumper black that is close also.