If you would like to cast a nice soft light on the hair of your subject simply use a softbox as a hairlight.
This image, created by Reza Mahmood, on our Studio Lighting Course was created using two softboxes. One was placed to light our model’s face, at approximately 45 degrees to the model, left of camera. A second softbox was placed directly behind the model and metered to be one stop less powerful than the main light.
As you can see, using a softbox as a hair light creates a soft and subtle lighting on the hair, nicely accentuating its texture and shape.