If any of you have played GH3 and got to the battle vs. the Devil, I recommend that you play it and use Slash as your guitar player (if you haven't bought Slash as a character, go do that first). If possible, try to watch the background of Slash (playing on an easier difficulty would make it more possible). The "dance" is when he bends down and spins with his guitar (it happens twice before the long instrumental). It is entertaining to watch and even more fun to play the battle on expert, sing, and imitate Slash's moves at the same time!
If you miss it, Slash does it on Impulse and some other songs too.