Were you trying to brush over Tamiya Flat Black? That's really the only one that I've run across that will not allow anything to be brushed over it. Of course I don't hand brush very much so I could easily have missed some of them.
I've just gotten to the point that if I see that I am going to have to hand brush over the top that I refuse to use Tamiya's flat black. Model Master works OK, and failing that I'll airbrush flat black enamel.