Well, basically, you kill yourself outside the door one round and then have your friend do it next. Then you go into the corner in the video and sticky jump. (You run at the wall until when you jump and hold forward, it won't allow you to jump. Then let go of the left stick, jump and then push forward. You you stick to the wall, but you have to hold back on the left stick to stay up). And then ta-da they pile up at the door!