Yea I tried Bill Parry's Valsalva Control technique religiously for years. While for the more severe stutterers, it does help you to get your words out and reach a certain level of fluency, it's still forcing words out by breathwork and the speech sometimes sounds forced, mechanical, effortful, and disjointed. Honestly the McGuire Programme is in some regards similar to Bill Parry's method. I wanted to speak as fluently and smoothly as normal speakers so eventually I didn't go along with that method.