I can related to that "high maintenance flock takes the pleasure out of raising chickens"
I did use the soak water gun, it works well for a little while, but I can only do it when I am in the garden, other time the bully hen is free to bully others, jump on them like a rooster so aggressive.
At the moment my bully hen Apple is quiet, she is molting excessively so she is often somewhere by herself, she is not hanging around other. Temporary break from bullying.
One of the hen copied Apple and head to jump on a few other hens, I chased her away and now I don't let her out with other in the afternoon. She is only out in the general garden by herself.
The extra work of separating them, managing and monitoring is not nice at all. I can not rehome or cull any of my chickens so I have to constantly trying to find a solution.