Been doing this a lot lately. What you do is walk up to a girl or two and open normally, but your opener needs a pretty damn good joke. If you make a good enough impression the girls will tell your friends, I've noticed 8 girls pointing me out to their friends as soon as they see me again, next time you see their friend, you are already opened because of your interaction with the other girl. All it takes to get the conversation started at that point is "Hey! You're XXX's friend, what's up?"