Matt Darcy shows how he sets this move up by faking guard. He also shows how to swing back and forth to get the move when your opponent initially blocks it.
Matt Darcy shows how to use the armbar to make space and recover to half guard.
Matt Darcy shows a slick armor from bottom side control when your opponent commits to holding on with head and arm control.
Matt Darcy shows an old trick he learned from Dave Camarillo. When late on the sprawl, shove the head and roll into the omoplata. You can also throw your leg into this position at the start of a round to trick your opponent.