Just your hair—nowhere else.
Damp hair, ideally after a shower.
If you idolise Don Draper and Fonzie, and Grease is your all-time favourite movie and you like to slick your hair. It also helps keep your hair super neat.
Just a little bit. Too much and you’ll damage your hair. Make sure it stays away from skin. It’ll clog up and you’ll erupt with acne.