My beagle x staffie can be dog aggressive. The only technique I find that works with her is distraction. She's extreamly greedy and will move mountains for a treat so the moment I see another dog I recall her (her recall is excellent something you must master with your dog) and make her sit for her treat. I then use watch me or touch commands and usually she's distracted enough to not even look at the other dog, or she might just manage a little growl while slobbering for her treat!!!

Have your tried clicker classes? I find it a really easy way of teaching them the watch me and touch commands, well worth finding out if you have any classes locally.