Setup like you would for a 360 shove it, maybe even have your back foot a little more like a pressure flip. At first it will seem impossible to actually spin it straight up and down, so what you want to do is start trying them a bit more 360 shove it style and less straight up and down. Then keep moving up and up until you get them straight up and down.
Ok, so you are in your stance, your back foot is like a pressure flip, so you can scoop the board. You front foot should be where it would for a 360 shove, but a little more back so you can slide it off easier.
Pop down but kick back at the same time. This motion is a lot like the pressure flip, so it might be a good idea to learn that trick first. Once you have scooped your back foot, take your front foot off right away and you should jump forward as you scoop. The board will do a cross between a impossible and a 360 shove. It might take a while to get the wrap around the foot thing going but it won't be to hard to do once you get it. Then catch the board with you front foot and stomp it.