Depends on what you're doing. When I jerk off my boyfriend, I can use spit, but it's rather something that needs to be refreshed in long sessions since it tends to get a bit dry and make the skin rather rubbery and so smooth movements are restrained...A simple solution for me is to get some hand lotion and just use a good thick amount of that. There's two benefits: A) It doesn't really dry up as spit does, and B) It makes the skin on the penis very friendly with the hands if you continue to do it like my boyfriend does. He does it every time he masturbates, and thus sometimes it's easy to jerk him off without any form of lubrication at all. This is just my opinion, though; spit does work, but the lotion thing is something you should try. Good for your skin.