Wow that's something else haha. It seems like he's using the nail on his right pointer finger to strum down, then following it with the thumb, then strumming up with his thumb, following up an up stroke with the right pointer finger and then repeat by strumming down.
dun duuuuun dun-dun, dun duuuuun dun-dun, down pointer, down thumb, up thumb, up pointer. Hope that helps
That was cool, isn't as hard as it looks, basically just copy what he's doing in the clip, but you'll have to feel it to get it to sound right.