Way back in my single days, I always longed to stroke myself for a hot lady, with the ultimate motive of watching them play with their pussies. I'd seen women play like this for years in adult movies, and it always got me hard as a rock.
I finally screwed up the courage to really try this, after discussing it with a lady friend (never did it with her -- it was that kind of friend relationship). My girlfriend at the time liked to suck my dick, then pull out before I came so she could feel my dick jerk as I blew a load on her, so I figured she would like what I had in store for her. I had my girlfriend lay down during normal foreplay, and started licking her pussy. This always got her going, and I just love to eat pussy. Then I put us into a 69 position so she could watch me jerk off. I placed her hand on her pussy and tried to get her to rub herself. That part wasn't getting much of a response, but she seemed interested in watching me -- that was cool.
Finally, when I knew I was getting close to blowing my load, I pulled her to a half sitting position, straddled her waist and started jerking my dick right in front of her face. I saw her eyes widen as I beat it for her, and finally shot a hot load on her big tits. She just keep looking at the cum, smiling and saying 'that's wonderful.' As I finished cumming, I was still hard, so I slipped my dick in her pussy and fucked her hard. It was one of our best sessions ever.