[Doug Nelson]

This tutorial can be used for at least three things:
to add texture to a picture to camouflage or disguise that the picture has unwanted texture
to add a subtle texture to any picture
to add grain to skin  [details]

[sergo]

Tell me, please, witch percent is Scaling:
Relief:
Light:

[Doug Nelson]

Unfortunately, this tutorial was written by Mig, who hasn't been around for awhile. But I suspect the settings you're looking for vary widely depending on the actual image.