Mikey Borup has a look at how to create vector trails for shape layers in After Effects. This type of an animated effect can be approached a couple of different ways. Probably the most common would be to use a plying effect, such as the echo effect in Ae.
The problem with the echo effect is that it can be quite intensive on your computer’s resources, which will slow you down.
Here, Mikey shows how to create the same type of effect using expressions in After Effects. This can be a great way to add secondary motion to shape layers in your animation.
Mikey Posts the expressions that are used in the tutorial: