In some cases documentation is hard to find but the usage is fairly self explanatory.
For instance, Body Light FX can be used to lighten (or darken) shapes.
In this example I've created a quick shadow effect by using Darken as an option and then inverting the effect so that rather than effecting the exterior of the shape the FX alters the interior.
Of interest: This FX gains some capabilities via use of the Swatch Viewer that can be opened at the bottom of the panel.
There we can scroll through the frames of the animation, create keyframes (all at once or individually for each option) and see the results in the preview window.
Disclaimer: I drew this for the purpose of this example and I in no way want to suggest this is the best or even proper way to use the FX. Others are encouraged to join in and share what they can come up with!