Don is correct on the applications. I just hand painted the props flat black (MM enamel) on my latest build a 1/48th V22 Osprey and the edges are glossy because I applied it too thick.
The best dead flat black to brush by hand is Humbrol, but has to be mixed every couple of minutes if brush applying.
If you airbrush Tamiya XF-1 it will go on dead flat. Brushing anything by hand in any color has a whole set of problems that can occur on that learning curve.
Always mix well with patience. You don't need to buy a mechanical tool to do it. I use a slim paintbrush handle.