Hi,
Here is a dog head sketch i made in ZBrush in about 2hrs. It was fun not working from a concept just working in free style to see what kind of head created. I used a lot the clay buildup brush, move brush (topological and regular). After working on it a bit i called it "wolf".
I found it helpful to sometimes use the clay brush to try to add appealing curves to the sculpt. When i was starting the sculpt i would sometimes flip over to decimation master to simplify the mesh before making tweaks then re-dynameshing.
I also found it really enjoyable to work in free-style to sketch.
Hope you enjoy.
Thanks,
-Nate