ZBrushCentral

As a hobbist, I made my first bust and I am loving zBrush

Hi, I am a first time poster here on zbrush central. I got my zbrush license a couple of days but I have encountered zbrush before through my path of education. However, I am pretty new to it and it has been many years since I used it before recently. This is my first attempt at a bust. I have learned much during this little project and look forward to start my next one.
As I am a learner, any push in the right direction is much appreciated.
My use of materials is very scuffed, and I know this, but not sure How I can make the model use different materials in a nice and clean way.

Hopefully, these links to the images work,

Imgur