So, what is this new-fangled photography technique?
I’m not sure if it’s new, but it is the first time I have tried it out,  works pretty good if you can get the settings right. To set it up you just tell the flash to sync to the 2nd curtain. On the flash, this is indicated by the double arrow. Below is a brief overview of setting up the camera and flash.

• Choose a location where the ambient light is behind the model
• Expose for the ambient light
• Aperture f2.8 – f4
• Shutter speed 1/8
• Adjust ISO to help balance the background exposure 1 -2 stops below correct exposure
• Now introduce the flash and alter the power to suit
• Lock focus on the model
• When shooting, move the camera and take the shot

As you can see the background is blurred, while the model is nice and sharp.