Well shit, that's really good! If i am to channel my inner nitpicker, here's a few things: If you're going for anatomical accuracy, the skin on the dogs head shouldn't be perfectly level with the skull. Also, the skulls nose hole should be a bit further backwards.

Considering that you DIDN'T mirror this (... i think), though, level of (implied) symmetry is pretty damn impressive! Also i love the shading, mmm.

Also, regarding delicate shading, i'm not entirely sure what you mean...? 6B isn't exactly what i'd call delicate, but it is lighter than 9B, for sure. Do you happen to have an example? I don't want to bore you with entry-level tips (read: most of what i know) that you're already familiar with, but i also don't want to pretend to know something that i don't. :v