I looked him up to see what advice he was giving, and personally found it rather generic. Things like having a positive attitude, remaining relaxed, and not overthinking what you are about to say certainly will help lesson a stutter, but they aren’t always actionable and, even with the most iron of wills and the best of attitudes, I don’t think a stutter is something that can be “cured.” Even CC stutters occasionally in his videos, despite curing himself. That being said, what he’s been doing seems to have worked for him, and he doesn’t seem to be trying to sell any self-help books or magic fix-it vitamins insofar, so I don’t think there is any harm in taking his advice if you feel it would help you.