As far as dog on dog aggression, I fortunately have not had too many problems: Annie is very polite with other dogs, even those who come bounding up to her while she is on leash-- and I've found it very helpful at that moment to simply release her, so she is free to move off and greet the other dog. At the same time, I am able to protect Dottie while Annie keeps the other dog occupied. As soon as I explain to other owners that Dottie has a problem with fear-aggression, but Annie is good, they are very good about helping to re-direct their dogs away from Dottie.
Occasionally I do meet an owner who is completely unconcerned when Dottie snarls at his/her dog, saying, "Oh he'll learn to back off after he's been growled at enough times." 
