watch Bridget Sloan's dismount
Bridget Sloan finishes 4th on Uneven Bars - from Universal Sports - YouTube. you hold the hollow/slight pike past the bottom, then open/stretch downward then lift the feet/hips then open again. she does it perfectly. and this is the "slingshot" technique and most often used.
the drill is simple. you hang on the bar. no swing. then you do 3 beat taps. on the third and when when the feet come forward, you peel and drop to your back. and preferably on to a soft mat or a mat on loose foam.