Two glass painters from the UK have this web site and make periodic postings about various aspects of glass painting.....anyone can "subscribe"....they gave a workshop at the AGG conference in Bry Athyn this past summer.
I purchased the instructional materials from Williams and Byrn and strongly recommend them. They are full of very useful advice.
I also attended the training at Bryn Athyn. These gentlemen are excellent instructors and delight in sharing their expertise.
By the way, Kenneth Leap was instrumental in bringing the Bryn Athyn class together. I'm glad he did. He also contributed greatly to the class experience by sharing his knowledge of the Glencairn museum medieval glass collection and the Bryn Athyn cathedral.