You use joints that are needed to do the flip, usually for normal people, they flip somebody by using the opponents momentum to make them flip themselves, for experienced player, they first get momentum for the flip wether it is upward or inward etc., then also use that momentum to get the opponents off their feet, when you have full control of the opponents, thats when you use your joints depending on how you're positioned, placement of feet etc, to try and flip them. I've told you what to do, you have to figure out how to do it, this also helps you create your own style of fighting, good luck.