How can I have Mission control, but just for one application? I have tons of windows open, and would like Mission control to only show the windows for one application.

How can I do that?

Note: I know that I can "scroll up" on the bundled windows for a particular application in Mission control, and the windows will "expand" a bit, but it isn't great.
That's called “Application windows” in System Preferences → Mission Control. There you can set a hot key to activate this. If you have a track pad, it's also available via four finger swipe down.