hmm..well you can try the non-blending method of shading. most artists use that one anyway. its where you basically just use the brush only, and select colors to make your gradients. if your pressure sensitivity for your tablet (if youre using one) is working properly, you can press harder and lighter to make the shading and smooth it out by selecting the closest colors/shades. There are also a ton of brush packs on deviantart that you can experiment with. This is a pretty good tutorial on how to do the shading i mentioned. She explains it way better xD