Masturbating with your woman is one of the horniest, if not the horniest, of all activities. I have done it with many women, sometimes on a no-strings-attached basis for women who really want to watch a guy pleasure himself. Many women enjoy watching, but they're afraid to ask. ASK, as it is erotica personified. My wife particularly gets off watching me ejaculate, especially when it is a real spurt-all-over-the-place affair!
Caressing your balls with the left hand while stroking with the right can send you into orbit. Starting to feel horny, so must go!