ditto on Stuka's comment. for myself Acrylics presented too much of a barrier in drybrushing so I bought a few of the basic colors (brown, black, silver, gray etc...) to drybrush with.
Karl (KJ200) does great work, so try his way and see if it works for you. I was too lazy and took the easy way out haha...
Good luck!
Oh yeah --- I had better luck drybrushing MM acryl than Tamiya... tamiya seemed either to flake like you said or "gob" up in places and look ugly...