Heh. Got me experimenting pretty much all evening. Basically, alongside the specular-only spot light (don't forget to point it at the skullcap or the primary hair group), working on the materials for the hair will give you all sorts of variations. In particular:

Specular_Color: I've experimented with this both as white and as a bright version of the overall hair colour. A lot of folks use gray, but I don't think that would have the effect you're after.

Specular_Value: Even if everything else is set up in Alternate_Diffuse, you can turn this back on. I've had it cranked as high as 5.0, but depending on what else is going on, for the sort of look that Randym had in the initial post of the thread, probably somewhere between 1.0-2.0

Translucence_Color: seems to affect how the hair looks between strands.

And of course, the Specular_Color on the Hair node itelf.

The other thing I experimented with in a couple renders was low level Ambient_Value ( 0.05-.0.2), with Ambient_Color set similar to specular. It creates an interesting effect.

The point of the exercise here is not realism, obviously, but getting something less real but arguably more dramatic.

Note: you want to make sure you turn off "Light Emitter" for each hair group in the Properties tab.

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In the render here, I've gone pretty dramatic. I'm using the Sat in the HSL colour settings advanced tab to saturate to a pretty bright yellow (which again, is of course not very realistic).

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Hardware: AMD Ryzen 9 3900X/MSI MAG570 Tomahawk X570/Zotac Geforce GTX 1650 Super 4GB/32GB OLOy RAM

Software: Windows 10 Professional/Poser Pro 11/Photoshop/Postworkshop 3