I don't really feel like elaborating, so this is going to sound choppy...
My style of play with the BM is pressure. CONSTANT pressure. Harass straight from the beginning and keep on nagging him, so you keep him in his base, steal exp, steal items, kill heroes, pick off weak units (archers archers archers archers) etc.
Raiders/shaman for stunning units, Naga or TC as 2nd hero, etc etc
I'll try to elaborate on this tomorrow and maybe give a replay