I'm surprised to hear so many success stories about sand. It must vary by location. Personally I've found sand to be an absolute waste of time (or worse). It gets washed away before it has a chance to become part of the landscape, and washed to places I didn't want it. I fill low spots with clods of black dirt that I harvest from high spots, break it up get it wet, stomp it down. For a few weeks after it looks like the aftermath of one of those pimple popping videos, but it grows back in fast enough.