I wanted to take a minute and talk about getting into Zbrush. I've had people in Real Life and online ask about getting started in 3D via Digital.
Here's my take on it. Just get started. Use Zbrush and dive in. Zbrush is very traditional in the sense of sculpting in Clay. In fact learning Zbrush teaches you how to use Clay (traditional). It also works in the reverse (Clay to Zbrush).
So here it is folks. Don't say you want to learn Zbrush for 3D modeling. Just say I want to sculpt and draw in 3D. Don't worry about polygons or how to box model. Just jump in and create like you would with Clay. If you give an 8 year old clay and say have fun. The 8 year old wont ask questions they will just have fun making some thing. This is what you need to do, go back to your 8 year old self and just have fun making some thing.
Refinement will happen naturally over time as you keep at it. The only thing about Zbrush that is hard (at first) is the UI. For this just go to Zbrushes website and watch the video's on UI. Once you have a small grasp on the UI start having fun.
Now, what are you waiting for just create. Above are my very beginnings in Zbrush. I've made only 3 or 4 sculpts and this is where I'm at. I didn't worry about polygons or worry about if I'm good or not. I just said I want to sculpt and have fun.
If you just channel your 8 year old self, you will have fun. So just create and have fun. These are my tips.