That’s very specific and I understand what you mean. I am not sure how mindful of this mechanism I am in the moments of stuttering but, I would say whenever I am prolonging a word I activiely am trying to move on to the next coming sound that I need. So, if I am saying “My” and I prolong the M into mmmmm I then try to focus on the sound of the y to release my lips from the m and begin the y.