Janet's question. Her dog is just one color. For a black lab for example, I would look for a strong source of light (like outside in bright sun)which would show some shadows or shine and use those. Pretend there is shadow under the head on the neck. One side of the face would be darker and the area around the eye is deeper and would be darker. It's as if you are shading the picture when drawing in black and white. I would do the same for a white mountain goat or sheep. Hope this helps.
The next post will be Wednesday. It will take me a while to prep for the next step and work gets in the way!