Seriously, what are any/best ways to tell, when meeting someone, if they are into oral, especially into letting you fuck their mouth.

I thought of this after being out at bar, and me & buddy met a couple girls. We were going to leave with them, and my buddy asked me which one I wanted. I responded "the one that would let me fuck their mouth the best". or something along those lines.

I wasn't into either really and was just being good wingman for my buddy who was into them. I picked wrong and wondered if he got the 'good' one. He left for training camp after that night, so I never got to ask him.