I highly recommend International Bonsai Master Michael Hagedorn as an instructor of Bonsai. I have taken a workshop from Michael it was a great experience and he is a very skilled instructor. Here is an article (Student Work at Crataegus Bonsai-)  written by Michael about some of his current students. I have posted the article under Michaels Bonsai Master bio, list under Bonsai Masters, shown under Bonsai Basics.  Photo below courtesy of Crataegus Bonsai.