I don't have experience with broca brothers. But last year I watched a [Ted](https://www.youtube.com/results?search_query=broca+brothers) tv show of them, and all YT video. As far as I understood, they help analyze unhelpful beliefs/attitudes in step 1, and in step 2 they focus on pelvic breathing to discharge the emotional or fight flight freeze. In my own opinion, at this moment of time I'm not interested in this, because it seems counter-productive towards building tolerance. If I remove the tension with breathing then I don't learn to tolerate it, at least that's my experience. However, since they were able to recover from stuttering as an adult with this method, maybe you can try it to see if it works, and then give a review on reddit.