My bosses' Sheltie is - no big surprise - a barker. They have gone to several trainers, and the one I think who was best came to the office, where Sheltie comes to work, as well as to their home, to see the environment and work on specific solutions. Of course, if the humans don't follow the training, the dog cannot be expected to. It is true that you need to train the people to respond consistently and appropraitely. Otherwise the dog won;t have a clue!