Boog sounds just like Lola. If a stranger approaches her, first she backs away, if they continue to approach she will growl. I admit sometimes she realllllly scares me. This behaviour didn't start with her until she was 6 months old I think. I'm pretty sure I posted about it here. I'll have to see if I can find those old posts.
But basically what my trainer started getting me to put her in a sit while strangers walked past and threw treats at her feet. No eye contact and no words. Then we progressed to them stopping in front of her, throwing the treat then continuing to walk. You gradually work up to the stranger being able to stop, give her a pat, give her the treat instead of throwing it and then walk away.
I know finding a stranger willing to do that can be difficult.. My trainer used her family and friends. But it does work. Lola now looks for the treat and doesn't growl or try to hide. At home is another story thought.
Too bad you didn't live closer.. I would soo be willing to help you out.