Two types of sky portal, one where you see the hdri image and a second which just directs the light values for the hdri minus the image.
I sometimes use clay as you describe, it depends on how the mood takes me. Right now my pain levels are on the high side so I tend more to the experimental side and this series is adding one elements at a time a little bit more extreme than I usually do. I have a LOT of time to kill.
Emitter Types Twilight.jpg