have your partner get on her knees and put her head down on the bed. It puts her in a position that allows your penis to better hit the G spot. But why would you want a "fast" one? No woman wants a fast one.
My first question is, are you trying to give yourself a fast orgasm or your partner? or both? . . for a guy, I believe it is better to have her on her knees, like she suggested, or you could have her on her back with her legs on your shoulders... For a woman, I think it all depends because every position works different for each female. Whatever the position is, rubbing her clitoris should do the trick.