well.....hang from the bar (hands can both face forward or one forward and one backward (like holding a pole), doesn't really matter). bend drive knee (right if righty, left if lefty;like take off), get a
little swing going and simulate a pull over without actually coming all the way around the bar. hips should come straight to your hands and you'll end up inverted like on the pole. be sure to use and keep your trail leg straight just like you would when vaulting. don't bend your arms and pull in order to get upside down. it's difficult to get the timing but once you do, this drill is very helpful! Someone can probably explain it better, but that was my effort!