We got a very fearful Schäfermix. The dog school could not take her completely the fear of other people and dogs. Each of you came too close was expelled with energetic snarl.
I put her collar and trained every day with her. After 3 days, the first noticeable change was already occurred and now after 2 months it has even relaxed when barked and growled.
But as I said, it is working daily with our dogs without the nothing works. Because most especially, the retracted Verhanltensmuster need to be changed and which can no collar in the world.