I swear by two things. First is phrase repetition woth speed. For me, I used to say, "rubber baby buggy bumper," until I could zip through it. Second is ventriloquism. Ventriloquists use different mouth positions to make similar sounds. I feel they help focus on breath control, mouth feel, and being aware of words. I'm not a speech pathologist though. I'm just some guy who figured out a way to control his stutter when the "professionals" couldn't. YMMV.