Single shot, dragged-shutter Second-curtain (rear curtain) sync flash on-camera, rotated on axis.
Set your camera's rear curtain synch so that it fires the flash at the end of the exposure, then set your shutter speed slow like 1/10 or slower (up to a second or two)
Push the shutter release while rotating the camera, and it will fire the flash at the end.
This will combine bright light streaks and a clear picture of your subject.
Single shot, dragged-shutter Second-curtain (rear curtain) sync flash on-camera, rotated on axis.
Set your camera's rear curtain synch so that it fires the flash at the end of the exposure, then set your shutter speed slow like 1/10 or slower (up to a second or two)
Push the shutter release while rotating the camera, and it will fire the flash at the end.
This will combine bright light streaks and a clear picture of your subject.