I only have a box blade, and use it for two basic functions: leveling ground and pushing material. The unique thing about a box blade is that it has a front facing and a rear facing blade. Depending on the adjustment of the top link, the box is tilted so one or the other blade is lower. If both blades are set to an equal height, they float on the surface and just push loose material rather than cutting much. For instance, going forward, the rear facing blade floats over the ground, preventing the front blade from digging in. This is real handy for moving loose material without gouging the surface. For leveling an uneven surface, I find it most useful to back up with the rear facing blade set slightly lower. The front facing blade floats on the surface and limits the depth of cut to something manageable. Meanwhile the rear blade cuts off the high spots and provides a flat surface for the tractor tires to follow. Whereas when going forward, the tires roll over the bumps ahead of the blade which makes the blade cut unevenly.
-Bill