When I was in my twenties, an ex-girlfriend called round to see me. We had always been very open with one another about sex, and after a while the conversation got round to her recent experiences. She told me about being picked up by a guy with whom she'd spent the weekend. She told me he'd had a lovely big cock, and it had felt like an iron rod going into her.
I was aroused, and asked her how big it was. She grasped her hand to show me the diameter. I was so turned on that without thinking, I just took out my cock, which was rock-hard by this time, and told her I was so turned on by what she was telling me, I had to have a wank. She just carried on with our conversation, providing more details of the sex they'd had together in response to my questions.
Within a minute or two, my cock erupted with a huge shower of sperm. She clearly enjoyed seeing my excitement, and my finale had obviously left her aroused too. Before long, I was masturbating her while playing out what I knew to be a fantasy situation that had a strong effect on her.
She'd told me a while ago that when she was younger, a male friend of her parents had rubbed her cunt through her knickers in the back seat of their car while they were on a long car journey, and that after that, she'd masturbated to fantasies of being touched by men in various ways. So I role-played the car situation with her, then a bedroom situation. She eventually came to a shuddering orgasm, then told me that it was the first time she'd ever been masturbated to an orgasm by someone else, something I'd never been aware of while we were going out together. This is a true story, exactly as it happened.