Trust me I know how he feels. I'm not so bad with mine, but my worst is when I was a cashier. I found that I get hit hard when I had to say the total and a number that is 50-59 is in the total. Those numbers make me hit a brick wall hard and I have this head movement that I do that is embarrassing, but is the only way it helps me. But I have found that when it was busy and I wasn't thinking about my stutter I found that it happened very few if any times. So I've found that if there is a way to keep myself occupied it may not happen as much. I've also heard about actors who have stutters like Morgan Freeman, but apparently what works with being an actor is that you feel like you play a different character and could potentially help with it. Not sure if drama is his thing but it's something I've heard. Have a great day and again I hope your son feels better!