Below is a recent photoshoot with a Volkswagon Golf GTI ClubSport 40. This shoot was of particular interest to me as I'd been looking forward to an opportunity to develop my light painting skills.
We scoped out several areas and had to wait for the ambient light levels to drop to the point where the continuous led lighting would have impact.
We shot multiple long exposures (approximately 15secs each) varying the surfaces I painted and then produced a composite in post-production using layers and masks in Photoshop. What you see below is a mixture of up to 6 layers and some reasonable time blending and toning.
With light painting and composite post-production, it's particularly important to keep the camera from moving, even a little bit can throw off the registration when organising the layers. A good tripod, manual focus point, and a cable release or timer to release the shutter will all help in reducing any movement.