Learn how to sing. When you learn to sing you learn how to use your vocal chords and diaphragm properly. Which translates to regular speech. Worked for Ed sheeran and a few other singers I can’t think of it. Worked for me. If I don’t sing for awhile my stutter starts to come back. So I highly recommend it. Also working out helps a lot too. Something about the regulation of dopamine and serotonin. CBD is only a chemical at its core. You have to literally reside your brain to be fluent. Easier said than done I know.