3D Camera Rig - Stereo 3D - lights & shadows

In After Effects, I am making 3D animation that I want to export as anaglyph. I know how to create a 3D Camera Rig in my original composition, which then creates a Stereo 3D composition that I can export as anaglyph. I did a lot with lighting and shadows in my original composition, but none of the lighting and shadows show up in the Stereo 3D composition. I’ve searched around on the subject, and so far the only thing I’ve found is this (https://helpx.adobe.com/after-effects/kb/stereoscopic-3d-effects.html ), which says, “If you create a light in your main composition, that light isn't used in your Left Eye and Right Eye composition and not in your Stereo 3D composition either.” It then says, "Adobe recommends that if you need to add lights, connect the lights in the left and right compositions via expressions to their counterparts in the master composition." I don’t understand how to do this, or at least, my attempts to do this aren't working. Can anyone give me a better explanation on how to do this, or point me to a good tutorial that will walk me through the process? Thanks.