I'll go with the majority. What make you cum is the up and down movement. If a girl wants to do this just with her mouth, she's going to have to work very hard at it. Far, far better to cup his balls in one hand (or move further back if you're adventurous) and use the other to jack the shaft while you give all the mouth attention to the head.
I love the twist (hold the skin back gently; pull it back tight; add a twist of the skin around the shaft; repeat for as long as he lasts.)
So your hand is the power house and your mouth gives the delicate touches that make a BJ heavenly.
Good blowing!