Still mucking around with materials. I sort-of think we're going to have to go with painted-on brows: that geometry casts a shadow in Cycles, and so it all sort-of looks wrong.

Open to ideas... so far, I have the above shader for lashes, which works a treat, but there's nothing in proximity to conflict with, whereas with brows...

Monterey/Mint21.x/Win10 - Blender3.x - PP11.3(cm) - Musescore3.6.2

Wir sind gewohnt, daß die Menschen verhöhnen was sie nicht verstehen
[it is clear that humans have contempt for that which they do not understand] 

Metaphor of Chooks