Costal breathing is the base of all the techniques that are used throughout the course, but I really doubt anyone could use them unless properly shown how to, as I said, its a four day intensive course, so trying the techniques on your own would probably not work and makes you doubt the effectiveness of properly using those techniques. As for my stutter, I had major blocks (sometimes it would be 15-30 seconds before saying a word), and used many filler words.