I used to have a dog that had horrible separation anxiety that got worse as she got older. She was a horrible barker and would bark non-stop until we got home, at least according to our neighbors. We tried a number of different methods including the thundershirt, but none really helped.
Ultimately, this probably won't help all that much, but I can say that I do know someone who it worked for. They would use it for thunderstorms, and after doing some training to get their dog used to it, they said it really helped calm their dog down.