I'm no pro painter, but maybe I can help
If you want an example of a well-painted all-black model that's not too hard to do, look at the
GW Ravenwing squad. I'd show you mine, but I decided on blue marines on black bikes (mostly just because it had been eons since I had painted ultramarines).
If all you want is "tabletop quality", the Dark Vengeance how-to has some examples are painting black, but it's very rudimentary. Essentially you edge highlight with dawnstone and do corners with administratum grey, and judiciously use red, silver, and a dab of gold or copper on the weapons and doo-dads.
If you want to do black properly, it's very difficult for two reasons. First, for miniatures to look good, you need do accentuate both shadows and highlights. With black, you can't go any darker (as with white, there are no highlight colors). Second, if you look at a photograph of an object which is black -- whether it's a black car, cat, or coat -- there is actually very little that is actually 100% BLACK (just like there isn't much that's 100% white if you photograph a white porcelain cup). Even a photo of a matte black stealth bomber is different shades of grey.
For these two reasons, if you really want an award-winning black model, you'll have to inject some other color onto the model's base color, like brown or blue. You then have to blend shadows and highlights based on how light would fall on the model. The black on the model is even more believable and appealing if you can use object source lighting -- for example, if a power weapon that glows blue lights up a spherical area of a space marine. These are not easy techniques though!