Costal breathing (I did McGuire at 14) and exposure. Once I learned costal breathing method and viewed my stutter as a breath/block anxiety thing vs a mechanical impediment, I started doing school public speaking/drama/debating. By no means perfect but as an adult (25 yo) I stutter so infrequently that no one would ever pick it up as a problem. I started viewing speaking opportunities as something I had to do because they scared me. I was able to have a career in politics as a press officer with lots of public speaking and am now a ceo of a startup and my job is basically talking.