Well it all depends on what area his fetish is linked to.....

Does he like to feel hair on his body? If so just let your hair caress all over his torso taking note of which areas get the biggest reaction.

Does he like to feel it in his hands whilst making love?

Does he like to pull it?

Is he into hair bondage? To control you by it?

He may want you to cover his "bits" in it and please him that way.....