Martin is known as a great acoustic guitarist/singer and he has been mentioned previously on this forum.
Martin is, of course, also a fine frailer, and is frailing technique has been carried over into his guitar playing.
Below are two links. One to his banjo playing ( doesn't he have an unusual right hand), and the other link shows Martin doing a slide blues. Notice how he plays the turnarounds. That technique clearly comes from his banjo playing.
http://www.youtube.com/watch?v=D8wn3FLAM7Q