>>32929736for shading you should probably try pencil, brush, or marker, the defaults should be completely fine
are you using layers to shade or are you coloring all on one layer?
have you tried playing around with brush settings? like blending and density? the actual shapes change it up a lot too. here's a little tutorial to help explain what each setting does, I hope it helps a bit, I didn't explain whatever I thought was kind of redundant
if you have a certain effect in mind maybe I can help with that specifically!