well it's a bit more complicated then just slapping an animation around... but in essence as newt said ... timeline animation or just sprite animation ... and then have a pattern of actions hard coded in the event sheet for each "special move" the boss will do. the special move is also easy ... since it just repeats... no randomness to it.
the hard part will be to trigger the DAMAGE done to the player by the hands/other stuff + the way the boss takes damage.
but again is tedious event sheet coding and there is no easy coding... is just logical puzzling coding... like code what u see in that video... and put in events as u think things should work. there is no correct way of doing it, it's just doing it.
P.S there is no plugin/tutorial on it... it's just practice