I also posted a movie showing how I created a hippo head in 10 minutes. It is not really a tutorial, but it gives a quick overview of the Sculptris basic commands. www.youtube.com/watch?v=iX1l5k9KwWM
Very good, they (and particularly the hippo head) show what is possible when you know where you are going and are prepared to stick to your guns.
I am used to thinking in terms of 2D false perspective and would have been tempted to make the face beyond the nostrils narrower. As your work shows though when you get the 3D proportions right, there is no need to force the perspective.