Do you know what sets your dog off the most?
Is it possible to start far away from that trigger, far so that you can reward BEFORE the barking starts?
Here is the idea for a dog that goes crazy when he sees other dogs, you reward before the dog gets set off, see how close you get... go further back if you need to...
Funny this was meant to be more about a statement about the Myth that positive trainers don't train red zone cases etc... But it also shows nicely the idea behind how to train in that type of scenario. The REWARD placement becomes the interruption of the behaviour, so you don't reward the barking, but you get the treat in BEFORE the dog barks...
http://www.youtube.com/watch?feature=player_embedded&v=WjIoLNN1N4g
I also found this article helpful, Ian Dunbar is the godfather of all that is positive and sensible in dog training...
http://www.dogstardaily.com/training/excessive-barking
Maybe a few good ideas in here too:
http://drsophiayin.com/blog/entry/excessive-barking-why-some-dogs-bark-and-how-to-fix-it I honestly used this 'puppy push up' method, to get Toffee to snap out of it, get his focus back to me and to interrupt his demand barking for example... barking for attention, treats or out of frustration... Dr Sophia Yin mentions in here the collars also and why she doesn't recommend them
Also try to work on impulse control to get the dog to focus more on you and make better choices in her behaviour, I know it may seem unrelated but it works SO well to give a dog a choice and reward the correct ones, a dog will always look for you for affirmation that they did it correctly and that you will reward them for the right choices!
http://www.youtube.com/watch?v=ipT5k1gaXhc
I hope there is something useful in there... oh also, I have used the frozen kong filled with peanutbutter when people come over, for example... keeps his frustration threshold super low... once he goes to his safe spot, he gets the kong... even get the visitor to give it to him... keeps him busy AND associate good things in his mind when visitors come over, he gets some yummy stuff! His barking is based on insecurity, so the worst thing I did was to shush him, holler and/or made a big deal out of it... and yeah I made it worse because I corrected him with sound!!
Until I got involved with helpful instructors and I learned to be better... I am not judging anybody who has been through this and found other methods, but these were the best for me and my dog. I hope this can help you also
All these tips will take time and commitment, but one step at a time, if you give yourself a couple of months you WILL see a change of that I have no doubt.