Wanna add a sense of motion to a still photograph? Dragging the shutter is one technique.
Here's how to do it.
First, you'll need to be shooting in relatively low light – so you can shoot at a slow shutter speed. If the light is too bright, use a Tiffen ND (Neutral Density) filter.
Set your camera on Manual and dial in an exposure that's about one f/stop under the correct available light exposure. Set your shutter speed, for starters, to 1/8th of a second. Depending on how fast you move, you may have to increase or decrease the shutter speed.
Turn on your speedlite and set it to TTL.
Now.... start moving your camera from left to right (or vice versa or up and down) and while you are moving, take a shot. The speedlite will give you a sharp shot of the subject, and the available light entering your camera will be give you a blurred image of the subject and the background.
Have fun with this technique. It takes a while to get it right.
