My favorite way to paint with light is to use steel wool. Although it is time consuming and requires a few tools, the results are worth it. Below are instructions on how to replicate some of the following images.
Tools Needed:
String
Egg Whisk
Fire Extinguisher
Steel Wool size 000
Lighter
Tripod
Camera
The first step is really important. Find the right area and weather! Since you will be creating sparks, it is important to not choose a dry day near anything flammable
Put your camera on the tripod
Set your ISO to about 200, your exposure to 15 seconds, aperture to about 5.6, and any white balance you want for varying results
Your settings can vary depending on the time of day or place
Cut about three feet of string and attach it to the handle of the egg whisk
Open the steel wool and take a small 2-3 inch portion of it
Start to pull apart/shred the wool with your hands so it is not compact . This step should make it very fluffy
Take your fluffy steel wool and insert it inside the whisk
Have a subject stand in front of your camera and light the steel wool with the lighter
Your subject should begin to swing the whisk from the string in any pattern you desire, just be sure to not move the camera
After all the sparks fly and are captured through long exposure, make sure there aren't any sparks which created a threat i.e. fire.