Demo for painting

 

First, I toned the canvas using Rembrandt's Transparent Red Medium.  The reason I use it  is because it makes the final painting more luminous when it peeks through here and there.  I started by measuring the distance between the eyes, then using that increment to place nose and top and bottom of the head.  I started with the darks.  (Before even starting the painting, I did a couple of drawings and a study with oils)

 Then I started adding the white and grays, trying to include temperature difference to make it more interesting. 

 Finished up by adding details, lightening the ears, and adding the color.  I never met the dog in person, but the owner said the fur was black even though the photo looks more brown and white.