I always try to us TK to throw something explosive at him. Barrel, propane tanks, whatever. Does a bit of damage, always helpful.
Best weapon to take down a BD, at least IMO, is the chemical gun w/ electric gel. You just hit the guy with the juice and he can't even move or fight back. Just pour it on him and he'll be dead real quick. You definitely need the consumption rate upgrade for the gun though, or you'll run out of gel before he dies.
To compensate for the high consumption rate, open up your attack with the grenades or proximity mines. Throw a couple of mines in his path and as he comes toward you, BOOM then hit him with the electric-gel. Fight's over before it even starts.