My Westie is 11 years old. 
When we began walks in the real world, he thought it necessary to bark and get excited when we came across other dogs. 
Every time we went for a walk I knew at some point we would come across a situation that would cause him to bark and lunge, leaving me to deal with the aftermath.
By this point in his life I had gone to puppy classes, had in home private training and read lots of how to books.
One thing the books, classes and in home training didn’t cover was the embarrassment factor of being at the end of the leash of a barking, lunging dog. 
I continued my walks, knowing this would happen time and time again; setting him up for failure each time.
People would walk by, flash a sympathetic smile and move on, often with their ill mannered dog at the end of their leash. The fact that he is a smaller dog made it even worse as he would do this to any size dog.
You know what happens then, right? “Oh look how cute” is the usual comment.
One of my children was afraid of clowns as a young child. I did everything in my power to keep her from bumping in to them. Before birthday parties I would ask if there was going to be a clown and make adjustments as necessary. Often it was simply to say “Please don’t approach my child”. Problem solved.

I am not one to think of my dogs as my “furry children”. They are my dogs, my companions, part of my family. 
One day a switch flipped in my head. I wish I could say what triggered it but I have no idea. I just remember thinking to myself, I wasn’t going to put my dog in that position any more. It was something I had the power to control. Why would I stand by while he was so stressed? It just didn’t make sense any more. More importantly, I just didn’t care what other people thought.
I began to research. One of the methods I read about referred to “open bar/closed bar”. In a nutshell it is treating the dog as long as the trigger is present. The moment the trigger disappears, the treats stop. 
This is basic classical conditioning: change the emotional response from a negative one to a positive one by teaching the dog that the presence of the trigger (other dog in this case) predicts really good stuff.
On the surface, it looks like you are rewarding the dog for barking and lunging. Not so.

I never left my house without treats in my pocket. I began to cross the street when I saw someone approaching. I stopped wherever I was. I would go up driveways, walkways, grassy areas. I did what I had to in order to give the distance he needed.
He often would still bark, but he was able to take the treats. Over time, with many repetitions, he began to look up at me when he saw a trigger – bingo! That’s the beginning of a new response. 

The big change was me getting over being embarrassed at my dog’s behavior and taking the steps to change it.
Once I stopped caring about what strangers thought, I was able to make progress and be my dog’s advocate.