While it may not seem like the portrait has advanced significantly since my last post, I did put quite a bit of time on what I have done so far. My method consists of indenting fine hairs with my pencil, burnishing, erasing and then applying additional layers of graphite on top of the previous.
I continue (not always in that particular order) until the desired tonal value and level of detail is achieved. This may also require me to go back to previously finished areas to adjust the overall tone of the portrait.
I do find the process more time consuming on a white dog due to the fact that the images I work with are almost always of low contrast and the subtleties in the lighter tones or values are more difficult to adjust.