I have yorkie named Polo and he barks at every dog, He sees small or big so I know were you are coming from.
You know those little soda cans you can buy at they grocery store.
Buy some of those and put pennies in it and bring it on your walk. When they see another dog and start barking shake the can and use a cue word Quiet.
If that doesn't work whenever they bark turn around and go in the opposite direction. Wait until they are calm and then turn back keep repeating this until they get it that if they bark they get turned around.
I hope this helps you