Welcome to the forum, Donegal. Nice first post. Your sentiments echo exactly those of at least one other current member.
That's my experience with my dog agro Amstaff and the first time in my life I have had to deal with aggression. I didn't raise my Amstaff any different to any of my others and for some reason unkown to me, he just developed a hate for other dogs at around 5 months old, strange dogs that is, not my other two older dogs, he's fine with them as I guess my other two are his friends. So for my dog, the Cesar style training worked a treat which got his mind off the other dog and snapped him out of the agro state to be able to use positive conditioning on him from there. The other trainer's methods on my dog, could never seem to break down his attention for other dogs or reduce the distance between them and him where he would react. Nothing seemed to ever overide his focus on another dog and it was like once a method of correction was used to get his mind off the other dog, then we were able to move forward in his training, but until then it was like a loosing battle.