It's practice......they need a lot of practice to do something like that. At first their nose starts bleeding like there is no tomorrow and then once they get used to it, then they can do something like that.
I saw a tv interview with one of these guys and some of them do it for money....and some do it just because they feel like it...to show off to people. But mainly it's just tradition. They say that their whole family members do these things....so......lol......
but really weird and GROSS!!!!