Back some years ago when the glass scene around Seattle was more active and Momka used to have open house days at her factory there were many good marble makers in addition to John Kabuki that showed up and gave mini lessons. In addition John had regular classes as did Sabina Boehm, N8, Mike Gong, Justin Bagley, Misha and Matt, and others for far more reasonable cost than today. I have taken classes from John at least 4 times. Each one well worth the cost. What I have seen over the intervening years is the slight changes in technique these artists employ. So if you haven't taken a class from your favorite or another good marble maker then retake the class and you will learn the new refined methods they have developed.
The recent post of John's demo at Corning led me to a subtle change he now does that solved a long standing problem I have had and now do not.... as much
PJH