If you have the prerequisites, than Aerial Twist shouldn’t be hard at all. All you need to do is setup like you would for Aerial / Webster and then perform a B-Twist instead. But only AFTER you leave the floor. If you start the B-Twist motion too early it will kill your flip.
Swing your arms opposite to each other. The first one will swing all the way from the top behind your body, while the other comes from the back all the way to the top.
Your Backleg needs to swing up high. It will determine how inverted your Aerial Twist is going to be.