I had a severe stutter from a boy age 5 to about age 30. Then one speech therapist suggested it would help me get through a block if I pr-rrrr-olonged the fff-first sound. That helped a lot. Another speech therapist lhad me desensize from the fear that I might stutter. I did that by purposely pretending to stutter with everyone. That helped me relax and to stutter even less.