clicker training can be good with dog-dog aggression. if you have a friend with a dog they can help you.

fine a large area where you can train where disturbances and other dogs will not be a large problem. then get your friend and their dog to stand a good distance away from you where your dog is still feeling comfortable, get your dogs attention on you and click and treat when hes paying no attention to the other dog. Over time you bring this other dog closer, one step at a time, if your dog gets too uncomfortable take a step or too backwards and start again. It wont get solved in one day but its not going to overly stress out your dog and it helps you bond with your dog more. clicker training to calm your dog will reduce stress and cause your dog to associate other dogs with tasty treats. playing with him would also serve as a distraction when other dogs are about.

Click to Calm: Healing the Aggressive Dog (Karen Pryor Clicker Book) by Emma Parsons is a good book to read and to get you started