Proper way to ask a girl to give up a few of her beauty/product secrets?

There is one particular girl that I know that has the most amazing hair. I know her well and she is on my Facebook. She even got voted best hair. I want to ask her what she uses, but I don't know how to ask her. How do I respond if she says she can't? I don't want to come off as obsessive or weird. There are a few ladies I have subtly asked in the past what they used and they never responded, or evaded the subtle hint. Is beauty some secret code? I understand not wanting to give up info, but how do you properly get someone to tell you?