The only magic cure that I've ever found is work/practice! It is human nature to avoid things that are unpleasant, like walking your reactive dog by or around other dogs. But that's exactly what they need! If when you go out you only see a few dogs out and about, find a new location with more activity. What I found with both of my previous dogs who were reactive on leash is that while that initial encounter took the longest to overcome, we made greater progress by sort of flooding them with encounters - purposely going to parks or neighborhoods with many dogs. Once that initial excitement wears off, your dog meets the next dog more calmly, giving you more and more opportunity to reinforce good behavior. It is sort of counter intuitive, but it works!
It's not the size of the dog in the fight, it's the size of the fight in the dog. Mark Twain