as was mentioned before, get better at the game, if there was some way that a male could get a 'shortcut' into a womans pants just by being good at sex or syaing they are good, every1 would want to know it!
But my suggestion is to bring up relationships when talking to girls, then move on to talking about past relationships e.g letting her know that your past relationships were fight, great make up sex, fight, great make up sex... then go on to explain how you cant just stay together because the sex is good , other things are important, then qualify her about something you find important. By her agreeing with you that you cant stay in a relationship based on good sex, she is effectivly agreeing with the idea that you know good sex and therefore are good at sex.
stories such as this can be easily placed in interactions because women love talking about relationships etc as much as pick up artists!
hope some of this helps
slick