Danny,
I think that the hows of using a box blade is almost enough to fill a novel. I've been using a box blade for about 90% of the first 30 hours or so of having my B7500, and I'm just scratching the surface (no pun intended) of how to use it.
With that caveat out of the way, this is what I've learned (so far) /w3tcompact/icons/smile.gif:
Because the box blade has closed ends, it is great for picking up material from "high" spots, and moving it to "low" spots. The secret is in learning how to control when it's scraping versus when it's laying. I've found that having a hydraulic top link is the key. There is a very fine line between the scraping position versus the laying position, and can be best summed up by observing the relative positions of the front and rear facing blades of the box scraper. If the front blade is higher than the rear blade, you are in the laying position. If the front blade is lower than the rear blade, then you are scraping. With the hydraulic top link, I just modulate the top link up & down to control how the box is attacking the surface.
Something the box blade is not very good at (in my opinion) is in grabbing material from the side of the road (or wherever) an moving it en-mass to a parallel location. A good example is where your road has lost its crown, and you want to move material that has sluffed onto the shoulder back to the center of the road.
That said, however, and the box blade can take it from there.
Stand by for some sage advice from some of the other experts around here. I think I've already said more than my experience warrants. /w3tcompact/icons/smile.gif
The GlueGuy