Sorry for my late reply. The thing is that even my speech therapist wasn't aware of this method, so I wasn't brave enough to try it out. But might give it a shot in the future. On the other hand, the passive breathing technique helped me a ton, my stuttering used to be horrible now it's barely noticeable, a great technique, so I can recommend you to try it out. You can find the book about it: Stutter no more by Dr. Martin F. Schwartz.