I followed Joe Dispenza's stuff for a while. I used some of his guided meditations to help get through a period of high anxiety, getting into a receptive state of mind then visualising how I wanted to be. I didn't actually try it specifically for speech as that wasn't my main problem at the time, but it could be helpful. Basically, if you've tried law of attraction/creative visualisation stuff and found that it doesn't work, Dispenza wants you to be in the right state of mind before even doing that, which will make you more attuned to taking actions and making decisions that take you closer to where you want to be. How effective it might be for stuttering is, I suppose, up to stutterers to try out and report back, or for someone to adapt the principles and conduct a trial.