Friendly Reddit speech therapist and person who stutters here.......I recommend going to a speech therapist. Do your research and find one that is a "Board Certified Fluency Specialist". As a persona who also stutters I am I big fan of the various strategies and techniques. Just because it didn't work for one person does NOT mean it will not work for your son. Best thing to do is find a competent speech therapist that treats fluency on a regular basis. If you want to message me in private or continue on this thread I can help you find one in your area.