http://www.youtube.com/watch?v=l1m8d-X2AwU
i think bboy mathias does it better but....
i think what you're supposed to do is like keep your foot straight, not so like you're tippy toeing but that you have like your foot pointing directly down so that the shoe doesn't bend.
also, i'm just guessing this but...
when bboy mathias does it, he's leaning back right? he keeps one foot ahead for the first beat, the second beat is with the other foot in the back, so that as he's leaning back, he's falling but catching himself with the other foot, so it applies more pressure and your feet comes down faster. i dunno sorry if i was no help =O