I can see this happening a number of different ways. Although I’d enjoy being an active participant, I could also see myself simply being a resource for information, encouragement, support or something else.
I actually did this once without really doing anything but being there. A woman I knew in college hadn’t had an orgasm with a man yet. She and I were going out and one day she was feeling really horny but couldn’t have sex due to a yeast infection. She stripped down while stayed in my jeans. After some foreplay avoiding her pussy she crawled on top of me and rubbed it over my crotch. I was quite hard after we’d been teasing each other and she enjoyed the feeling of my jeans on her pussy. She kept going for a while, increasing her moaning and groaning until she went over the top. I didn’t appreciate it for what it was at the time.
