I had a gf who went in to the toilet and held my cock while I peed, she had no problems aiming, when I finished she didn't understand the shaking or milking to get the last drops out, so that was a bit of a battle, but a few weeks later she wanted to try again in a public toilet and did a better job. She did find the smell a bit off putting though, she felt it was stronger than hers.
Another time we both had to go so she sat on the seat and started to pee and I moved up in front of her and pulled my cock out and I pissed through her legs while she was peeing, it's was very erotic for both of us and after wiping my cock with paper she started giving me a handjob and I came in the palm of her hand.