Our first dog was a rescue dog that had come out of a terrific working Australian Shepherd line in Texas. One of the absolute hard requirements to adopt her was that we would commit to taking her through at least a basic obedience course, so we signed up at the local dog gym, the only local gym - there were no choices.
They used (parts of) Koehler, the slow way. We used a pinch collar and a long lead, and a lot of treats, and went very slowly. In total we spent probably 18 months in obedience classes, went all the way through advanced. We spent at least 30 minutes a day, every day, working on training.
It worked. She started out being the worst behaved dog in the class, to the point that my wife disavowed she knew me when I had the dog. But by the end, she was the best dog in the class and it wasn't close. And she turned out to be the best dog to ever live. She literally saved my daughter's life twice. We could let her out into our unfenced front yard and know, without a doubt, that she would scope out the property lines and alert us if anything crossed them but not go over them herself... unless the kids ran off, in which case she would tail them and bark when my wife called to let her know where they were. It was like having a third adult in the family.
It's been ten years since she passed, at age 15, and I still cry when I think about her.