Okay different anon obviously but! For simple shadow rendering like cell shading and all, you can just use multiply, for which basically all you need to do is
make another layer put it on multiply,
choose a colour (black for shadows usually but I personally don't use pure black, i mix it with another colour to make the shadow and the overall piece more vibrant)
Make the shadows with said colour
Decrease the layer opacity to where you feel like you like the shadows
Basically what multiply does is like it makes the colour on the layer transparent and like just a tad darker.
And for highlights you could use overlay or luminosity, experiment with them a bit and see which you like more
- master anon
OOH tyty :)))









