Compositing w/ Render Layers 2.8 Instructions

Terminology:

Scene Layers -> Collections, found in the top right outliner.

Render Layers -> View layers, found in the very top right corner of your screen above the outliner.

Instructions:

1. Check Render settings, Film, Transparent (so objects render with alpha), and Transparent Glass since there is a glass in this scene. 
2. Make 4 Collections: Orb, Other objects, Backdrop, Lights/camera and move the objects into each. (Reuse the existing).
3. Make 3 Render Layers: Orb, Backdrop, Other objects render layers. (Reuse the existing).
4. Change to the Backdrop layer.
5. Right-click the Orb collection, go to View Layer, select Set Indirect Only. The orb disappears, but the shadow remains on the backdrop. If you don't see this, go back over the instructions. This only works in Cycles, currently.
6. Repeat for the Other objects collection. Now you have a backdrop with light and shadows only.
7. Change to the Orb layer.
8. Uncheck (exclude) the Other objects and Backdrop collections. Leave the Orb and lights as is. Now you have an orb that is lit, on an alpha background.
9. Change to the Other objects layer.
10. Uncheck (exclude) the Orb and Backdrop collections. You have lit objects on an alpha background.
11. Render. In the render result you should have 3 layers exactly as described in #6, #8 and #10.
12. Switch to the Compositor and enable Use Nodes.
13. Add 3 Render Layer nodes and set them to Backdrop, Orb, Other objects.
14. Add a Color, Alpha Over node and connect Backdrop and Orb.
15. Add a second Alpha Over node and connect the output of the first, plus the Other objects. Connect that to the final Composite output note.
16. Render again and now you have four layers: The 3 described in #11, as well as a composite layer that should look as if you had rendered everything in one layer.