Is it possible that he's using the edge of his thumb right after the down stroke (thumb and radial side of palm Vs ulnar/pinky side of palm)?
When I rake downwards, my wrist naturally turns slightly anti-clockwise so that the thumb/radial edge of my palm is closest to the strings. If I were to use the pinky side of my palm, I would have to make extra effort to turn my wrist clockwise to dampen the strings.
Hi Paul, I've been thinking about this question for a few days, and have some ideas.
Firstly, remember that Griff says that this technique can sound really ugly when we're practicing it slowly, but we should "butcher it, loud and proud" until we get it right.
Secondly, it's in (really exaggerated) swing time; 1-uh2-uh3-uh4-uh1 the upstrokes are on the "uh". And the downstrokes (silent) follow the upstroke immediately; THEN we pause before the next upstroke.
I meant muting immediately after the uprake, but that cuts the notes too short and gives it a staccato sound, which is what I'm not hearing either.
I think it actually IS staccato, and I mute the strings on the downstroke with my picking hand, so the chords don't sound out for very long at all. As I said above, the downstroke follows immediately after the upstroke, then pause before the next upstroke.
How that muting happens, is that I "pump" my fretting hand, lifting the fingers off the fretboard, almost immediately after I finish the up-stroke. That kills those strings. Then I do the downstroke immediately and use the heel of my pick hand (between the pinky and the wrist) to mute all six strings. I don't "sit" the heel of my hand on the strings, I just slide the heel of the hand across all six strings. It's completely automatic, because I've been doing it like that for many years.
The mechanics of the pick hand go like this - on the upstroke I roll my wrist upwards while I'm moving my whole forearm up, so that the heel of my hand actually rolls in towards the strings. Then on the downstroke the heel of my hand is already close to the strings and the pick is out of the way, so I can slide the heel of my hand across the strings without striking any of them with the pick. Then my wrist turns downwards so that the pick is ready to hit the strings on the upstroke.
You can sorta practice that motion right now - hold your thumb and finger together like you're holding the pick; raise your picking hand up and rotate your wrist out, push the hand down and rotate your wrist back in. That's a very exaggerated motion, but it more or less mimics what you're trying to do.
Sorry to be so long-winded, but I hope this helps a bit.