MikeC,
You have several flat black options: you can use restoleum small brush can/spray can which I've used since the 1970s on models. Available at walmart or home stores.
My favorite flat black is Mr hobby flat black which is lacquer paint but is harder to find but available in hobby shops or online.
Or you can use any black paint (or craft paint at your hobby lobby) and use testors clear dullcoat, krylon clear Matt finish or even a flat varnish topcoat for desired flat black finish.
I use all 3 three at times.
Just a few suggestions...