I've worked my way there only once, with chicks I both banged before. I wouldn't go at it with 2 stranger pussies... kinda awkward when you wrap up.
Plus you hit the big dilemma at the end; Who do I finish off with? 
I am gonna sound the average douche getbigger, but I have done it many, many times. I lived with a couple of strippers, they would always bring their friends home. If the bitch is not a stripper and I get her to do it, whether it be with her friend or a stranger, they always end up sitting there pouting while you are pounding the other girl. Every fkn time.