Clipping/cutting nails

Hi all, I've recently found this site. I was a long time user at Pets.com before they left the net. Anyway, I have 2 Dobes and it seems like their nails grow very long in a very short time. Has anyone out there used the nail "grinder" for dog nails? I've only seen it used by the people that "show" their dogs, however, most everyone else seems to use a "cutter" or "clipper" of some kind.
Problem: Dobes nails are black, which makes cutting a bit of a problem. Going to the groomer for this is getting expensive. Any thoughts???
Thanks and I look forward to chatting with other "dog folks".