Although a Wacom tablet and pen are very comfortable to use, nothing beats a technical pen for sketching.
Herdwicks are a natural subject, for of all the sheep I've seen, the Herdwicks have very distinctive faces. These two cuties were originally photographed on the way to Far Easedale (Lake District, U.K.) and sketched (with the help of a wash) in leisure at home.
To free my hand, I prefer to choose a photograph of somewhere or something and proceed to sketch away till I'm warmed up. Of course, some tens of thousands of lines later, I'm more ready to read a book than do another drawing or painting.