I'm late to this thread i saw it and forgot to reply.
My DP is a 'talks to fast for his mouth' stutterer. E.g his mind races ahead of his mouths ability to produce the sound/words. His is quite pronounced, it can talk him 6-8 repeats of part of the sentance to say something simple e.g 'take your book and put it on your book case' would be 'take your book and put, and put, and put, and put, and put it on your book case'. Occasionally i touch his arm or something and it seems to help him slow down, but for the most part i do and say nothing. He is perfectly aware of what he is doing and also completely inable to stop it.
My DS4 during spurts does the same thing, expect 2x as bad, it can take him ages to get out something like 'can i have some juice'. I do the same with him just wait patiently till he finishes. Or if he gets very frustrated i gently tell him to stop and try again.
http://www.stammering.org/parents_info.html