While at my last job I created a Hair Highlight shader our 3D characters. I looked at a number of other pre-made hair shaders for inspiration, most of which follow the Anisotropic lighting model. A lot of them had weird lighting and shadow artifacts or suffered from Z-fighting issues. I tried a different approach for as I wanted to create highlights based on light angle while mostly keeping the standard lighting model. Using a custom implementation of fresnel effect I was able to get this custom highlight. By adjusting a custom highlight value and the Ambient Occlusion power I was able to get the look I wanted. NOTE: the model on the left is the Unity Standard PBR model (with backfaces culled) and on the right is my shader which I made double sided with correct lighting on both sides.