I sculpted this head from a sphere in Curvy. After blocking out the basic shapes (red head) I loaded up lots of reference photos in an image viewer program beside Curvy on my monitor. This helped me add some individual character to the face. At this point I used the soft move tool to drag the face into shape and sculpting brushes with very low intensity to carefully refine the forms.
Finally I traced over the major angles on the face with the Pinch Brush. This sharpened up the shapes to create a well defined mechanical look while keeping the character and smooth shapes of the original.
See the full Robot Model here