On the other paw, when I checked with texture-mapped figures, including the default human texture on Posette, I was getting the same effect. So it's not skin brightness. What did seem to make a difference was changing the Softness setting on the Fresnel Spot node. In the tutorial, the Softness is set to 0.00000 I adjusted the value to 0.5000 which matches the other Spot nodes. The blotchiness vanished, for all the skin tones I tried it on. I'm not saying that's the best value to use, but it seems to be the setting to tweak.