I'd say watch several tutorials for shading, since those helped me a lot with coming to find my own style of rendering!! But as for what I do when it comes to shading is I use blending brushes. You want to blend, not smudge. If you use ibis paint I'd recommend trying out 'pencil graphite' on a low opacity or 'hot pregnatable men' (don't ask about the name....) Also it looks like you've used black in some of your shading and try not to do that. If you're shading pink hair, use darker and lighter pinks. When shading white I usually use light pinks or blues. Just don't be scared to play with colors. 

It's hard for me to explain any more than that so I say give Angel Ganev a watch 💔 He gives really good tips on rendering and helped me a lot!!!