You can kick back and watch this screencast, or scroll down for a more literary overview.
Simply select the properties that you wish to add expressions to, choose the type of easing from the popup menu, whether it should be “in”, “out”, or both and click Apply. As of version 1.1 it’s possible to apply the expression to all keyframes instead of just the first two.
You can choose any number of properties (including different kinds), on any number of layers, and the script will add expressions to everything that’s selected.
Note: If there are already expressions on the properties that are selected, they’ll be replaced when you click Apply.
Types of easing
Regular easing (from most to least dramatic)
Expo, Circ, Quint, Quart, Quad, Sine
Back, Bounce, Elastic