My sister and I continue to routinely masturbate together. The last time we did it, was very quick. We were both just really horny I guess. I began by rubbing her outside of her shorts while she was lying on her stomach. I eventually brought my hands under her shorts and just gave her a very quick, but very intense clitoral orgasm. I just dry humped her bed and came all over my pants.
Recently, we took it a lot slower. I began by massaging her breasts outside bra and then by just playing with her vagina under her panties. I rub the top, her lips, I play with her butt and then finally make her take them off. My dick is poking out if my boxers all while this is going on. This time, she got a lot bolder and made me get an electric toothbrush from the bathroom. I used this to work her clit while I went in and out with my fingers. We literally exploded at the same time. I had cum all over me and she was soaked.
As I've said before, we've done this for years and have perfectly healthy, normal relationship. We just really enjoy mutual masturbation together and don't really have any plans to stop.