YouTube is full of trainers, many of them are horrible, but some are actually good and they'll answer questions, or schedule web consults.
Find a good one, and ask them.
My suspicion is that any behavioral training that doesn't involve you, and everyone else in your household, will be all for naught.
Effective training might require some boarding for the trainer to get a handle on the issue, and then then working with his immediate handlers on how to solve the human part of his behavior equation.
Get multiple opinions from different trainers, see if they overlap, and then move forward.
Here's one example of a good trainer with a YT channel:
https://www.youtube.com/channel/UC6vdCX3-G6oDGajvQFreLLA
He also runs boarding, training, and web consults.
But, please don't just take my word on his credibility. I'm just someone who's watched some of his videos, and liked what I saw, that's it's. I'm not a dog training expert, or a shill, so take my opinion for whatever you feel it's worth, or don't.