Someone please ANSWER ME!!!? ?

My best friend's girlfriend goes to my school. (my best friend is a guy and its an all girls school). He wants to know if she thinks he is a good kisser. He doesn't want her to know that he wants to know. He wants me to ask her if she thinks that he is a good kisser. How do i do this subtly? How can it not just be a blunt question, but play into and go with the conversation? Any help at all will be great. Thanks