Reply to Ending a set?

Does anyone have a clue on how to end a DJ set?
I keep hearing this great effect and I've played around with it but haven't mastered it. I've heard all big name DJ's use it in their sets; Steve Angello, Tommy Trash, etc. It's where you loop the end of the song and keep shortening the loop and it finishes on a clash/boom sample? Does anyone know how I can do this or what it's called?