I was waiting in the lounge of a parlour to see my then regular girl. She suddenly appeared, stark bollock naked, and said the guy in the bedroom wanted another guy to join in. She said that he would pay (a free cum for you was how she put it). She said he wasn't gay or bi and wouldn't touch me.
So I went in. Middle-aged tubby guy, sat on the bed, and quite comically we shook hands. She gave me a wet sloppy BJ while he watched closely, then he asked me to fuck her doggy, which I did. He was watching closely, having a frantic wank all the while.
He asked me to cum over her face, which i was happy to do ( ! ) The other guy grabbed her, and still with spunk running down her face he rammed his cock in her mouth. She sat up opened her mouth and the most enormous river of cum ran out. Outside of porn I have never seen so much .
Later she told me he never fucks her, likes to watch things (like her using dildos and so on) wanks off and cums in her mouth, always a huge volume.
My one and only MMF fun but not sure I'd repeat.