I'm not sure that there is a number of passes that will give you a smooth surface. Understand that a box blade is designed to recontour and move soil. The scarifier teeth are designed to rip the soil and the box is designed to move the soil. I've typically gone over the areas I've box bladed with a landscape rake the soil smooth.
Many people use a BB to groom their gravel driveways, I'm not one of those as mine is asphalt. I think there are better tools for driveway grooming than a box blade (see the posts above by SonnyP and the posts I made late in this thread about a similar implement from a differnet maker).
If you want to recontour a slope, fill in low spots with soil from a high spot, etc. then a BB is a great tool. But you will make repeated passes to move the soil. This past summer we redid part of our yard, there was a steep drop off of about 5' in one area where a new fence was going so it took me dozens of passes to cut back that slope. I was only doing a small area, perhaps 30' by 40' that I just wanted to change the slopes taper on. But I worked on it for a very long time, it would not surprise me if I made up to 100 passes on the area. Even after all that, to get the ground smooth enough to plant grass, I went over it with the landscape rake.
I'd also point out that how you have your toplink set will largely determing how much or little of a bite your BB will take. A hydraulic top link is a very very handy additon if you plan to use the BB frequently for projects.
I'm sorry but I don't have before/after photos.