I don’t know how it’s done, but I do know it can be done. We had a neighbor across the back fence who trained his dog not to bark. She was so silent that I thought she’d been surgically altered, but he said no, he just knew how to train dogs. The neighbor acquired a full-grown, rather goofy and very rambunctious second dog, and it took him only about three weeks to train him to be quiet. I wanted to know how he did it (and there was no indication that any cruelty was involved), but they moved away and I never got to ask him.