Finding the right trainer with the right philosophy is important (regardless of the breed). With a situation as yours, you need a trainer who is schooled in BAT (behavior adjustment training) not just an obedience trainer; and of course someone who follows positive reinforcement training. Ask for references from their students if necessary.
I once had a trainer who billed herself as a behaviorist but really she was just an obedience person and believed in yanking on prong collars (I quit after half the class).
There is also an excellent online program for reactive dogs at:
Look under Classes, then discipline and behavior. I took the "Dealing with the Bogeyman" class. Even though its all online, it made a BIG difference with my reactive male. I highly recommend it.