I'll add another resource, if you have one: your local Kennel Club? Our rescued Cattle Dog was dog aggressive: our local kennel club let me bring him to obedience class, knowing he would be treated "firmly" if he acted out. They were awesome - gave pointers, and even allowed a few super-friendly dogs to approach mine under carefully-watched situations. While we never completely trusted Jack around strange dogs - his aggression went from a 9, down to about a manageable 3. When encountering strange dogs, I could tell him to sit/stay, and he would, although growling with hackles up the whole time.....LOL!