This video shows how to create hair in Photoshop from scratch with the paintbrush and smudge tools only. To recreate this technique, I have found it best to use brushes in various sizes with a soft edge and the opacity at 100% but with the flow taken down to about 70%. After creating the initial lines use the smudge tool, and use a dry brush with many points at around an 80% strength. This will mix the colours together in the main section of hair and create the look of seperate strands on the end of the hair. Repeat this over to build up the effect.