I've got and tried both dermmatch and nanogen on my balding bonce and they can be fairly succesful.
I'm still going through a ''What style am I going to settle for'' phase right now, I've tried shaving it but growing it into a 3 cut right now and stuck some dermmatch and a bit of nanogen on and it can work on a buzzed head which I've done too.
Less is more would be my only advice. Dermmatch is probably better for shorter hair and nanogen/toppik more for thinning bald patches and thicker hairstyles as it's fibres.
My only issue with it is that if someone touches your hair, they'll probably have a dark/blonde/red/ whatever colour mark on their hand.
Best way is to experiment, buy some product and have an evening or an hour or so to yourself to test it and see if you like it or not. Also, try to test it under very bright lights. Many Supermarkets, Bars etc all have super bright lights so you want to make sure it's applied well under bright lights and blend it in. Nothing worse than it all sitting in one part on your head.
Good luck.
