You use a stick that glows like a torch bit like those things you see crewman using to help land/take off aircraft that they wave about in their hands.
Then you adjust the shutter speed. If you use a fast shutter speed at say F1, you get a clean sharp picture of the car. If you use a slow shutter speed, the car appears a little blurred, so it looks like it's moving.
Don't think it can be PSed properly though.