High-Speed sync (faster than 1/250 all the way to 1/800) has been a stalwart of the Nikon wireless system for a long time. It's built-in with the D200/D300/s/D700/D800, the D70/80/90/7000 and probably with the 3000-5000 series bodies, it's built in to the on-board flash. With these and the D2/D3/D4, it's simply using the SU-800 and most of the current and previous generation flashes.
Easiest way if shade, clouds, etc. aren't available is to simply use a TTL cable to your flash to get it away from the camera so that YOU boss your flash around, practice at your leisure, then go out with a wider-angle lens, move in closely and shoot away. Sometimes just that little and for some annoying built-in flash is all you need to lessen the harsh shadows.
It seems daunting, but with a little hands-on practice and a little bit a flash, the harshness can be tamed.