I've had loads of wg's fanny fart on me they all ignored it except one she laughed about it, I've never had them actualy fart though, although I've let a couple of silent ones slip out 
After a fairly lackluster start to a punt a particularly petite asian prossie gave me massive entertainment thanks to her pussy farts, the further in I went, the higher the note.
The only time I remember a prossie farting proper was a street girl, massive ripper but she followed through and filled her jeans. As luck would have it she was outside the car at the time and was genuinely surprised when I said no to a lift back. I seem to remember donating by wet wipes though.
