hi, the slide playing appears to be played on bess Lomax's Martin 6 string with a commercially made metal slide. It's excellent and like everything else he does is quite original sounding. When he played in "D" (his D which sounds Bb to us) he often went up the neck to the 5th and 7th fret. He is often erroniously credited with being a thumb and index finger picker like Travis, Davis, Everly (Ike) etc. Not so. He used thumb, index and middle. Glad to meet a few Leadbelly fans.