So i've used the pen tool in photoshop and i cant seem to use the after effects pen tool in the same way.
In photoshop you can click and drag the tool to create curves and then you can alt click on the point to kind of cut it in half so your next curve is unaffected by the last one.
Can you do this in AE? hope you get what i mean
Read up on how to use the mask tools in the AE help. It works similar, but not exactly the same.