All of these sculpts are one hour sculpt using Zbrush.  I begin with one of Pixologic base mesh and insert my own eyes, then start from there.  When sculpting these figures I try to focus on silhouette of the figures.  I try to achieve the most amount of detail with the fewest strokes possible since time is of essence.  I have found that these challenges has allowed me to explore other tools within Zbrush that I wouldn't normally used and to continuously thinking ahead while planning my next step.