In order to begin the process of coal tattooing, one needs the necessary supplies. As indicated by the photo below, a small chunk of coal is needed, as well as a few different sized styluses. You may even use other rocks, like this brick, but black results in the most contrast for skin. You will also need a small amount of water.
Once you have your utensils assembled, pour some water onto the rock and commence with the creation of the black paint. Scrape the chunk of coal in the water, until a thick paste is present.
Now, sharpen your stylus on the rock. This is important for detailing your coal tattoos.
Dip the stylus in the coal paste...
...And have at it!