Quentin Tarantino only directed one scene: the one where Clive Owen is imagining that Benicio Del Toro is talking to him. Robert Rodriguez did the score for Kill Bill Vol. 2 for a dollar, just because he wanted to do it. So in return, Tarantino did the one scene, and of course lent his name to the PR campaign. Mainly Rodriguez wanted Tarantino to to try out filming in Hi-def digital to try and convince him of the benefits of shooting with digital instead of film. Frank Miller was also a "director" insofar as the comic books were used as storyboards for the movies. So really even with all the director credits, it's still pretty much all Rodriguez.