This method is 100% taken from the Novabeast Substance Painter file but I want to archive it somewhere

<aside> ⚠️ You need to make sure you have baked most Mesh Maps on your model before applying the layer effects

</aside>

Fill layer

You can try inverting the light effect to make a fade from the tips for example!

Light Generator setup

Mask (can remove if looking too wrong)

The Fill map contains the AO map

Smart Material Download

https://public.sesilaso.com/WikiStatic/Hair Highlights.spsm