From everything I've ever heard, Dan's suggestion is what you're supposed to do. I believe it works for marble as well.

In fact, they talked about this on the last season of This Old House. They were installing marble countertops which stain even easier than granite (particularly the kind of marble they were installing). The demonstration was more aimed at getting rid of a wind stain, but I'm pretty sure they said it applied to anything. They applied the slurry, covered it in plastic wrap, taped the wrap to the counter (with blue painter's tape, I believe), and left it for like 2-4 days.

*edit*
It isn't from the episode I was talking about, but the This Old House website has instructions.