I have some knowledge on Clinics having started teaching them in 1981 and making a living do them in SoCal for a couple years. I have also taught them in 28 states or so. (BTW none in NJ but I did teach a few in PA including Bensalem in 97).
Greg Hill is not only a great rider, he is a great coach. Anyone including myself could learn from him. There are only a handfull (5) guys I would put at the top, when it comes to teaching BMX and Greg Hill is one of them.
And its not just for beginners. After one of the clinics I taught, one of the Pros helping caught me by suprise, saying he learned some stuff from me. Greg can point out little things you do and dont even notice and some of the little things you should be doing, but are not.
A huge part of winning is the mental challenges. Greg can help any rider focus and work on that as well as how to improve the basics.