Composite Effects

[Daygola814]

I was wondering if anyone has seen the "Once Upon A Time In Mexico" DVD where Robert Rodriguez gives that ten minute film school and shows how he did some of the effects. Mostly the effects of the cars hitting people, the sliding down the stairs scene. Anyone know how this was accomplished? I've been trying to figure it out for a while but haven't been able to. ANy help would be appreciated.
Thanks!
-Paul