One advantage to inks when painting black is to tint them. There are tons of 'black' things which pull towards one color or another. A little bit of blue ink, in particular, can add some color depth to a black paint job and, in my opinion, goes further than a typical grey highlight. Even so, Wolfenbaum's paint looks great and the ability to focus on other aspects of a model will quickly overshadow (no pun intended) a largely black, crisply highlighted model. When I look at thos handgunners, for example, I'm immediatelydarawn to the face and that striped leg.
The foundations might help some of those other colors to establish a cleaner base than, say, fleshtone or white on black. Otherwise, sticking to your normal paints and tossing on the occassional ink might cover you. Don't forget you can ink your other colors, too.