How to Mix Warm and Cool Grays

This week I posted two videos on my Youtube channel the one above is about mixing warm and cool grays. The next video which I loaded up yesterday is my first portrait of rescue collie Henry using only warm and cool grays. 
Henry does not like it when I am in the studio. I do not use the hairdryer but he still hates the swish of the water so I keep treats in my pocket and call him in from time to time . 
This is not great for my concentration but Henry needs this for now and he is food motivated so it is a win win situation.