Imparting Motion with Flash

I keep my flash set to "rear shutter", (I think some call it rear curtain), and to get motion, use a slow shutter speed, (1/30s in this photo), called dragging the shutter. So what happens is the shutter opens and is open long enough to record a movement then just before closing, the flash goes off, freezing the last part of the motion. It is easy with todays cameras.