I enjoyed watching this. Thanks for posting! I've been a fan of Sonny Landreth for many years. But I have mostly heard his electric slide playing. I saw him with John Hiatt and the Goners back in the late 80's.
It was interesting to hear how he discovered the technique of fretting behind the slide. I enjoyed this quote... "Once I became friends with guitar players like Robbin Ford and Eric Johnson, I decided I would concentrate on the slide guitar". Seems like a personable fellow.