Casting for Wayward Sisters, the spinoff to Supernatural, is off to a great start with the addition of Briana Buckmaster according to SpoilerTV! Buckmaster is best known as Sheriff Donna Hanscum. She first appeared in Supernatural’s ‘The Purge’, where she crossed passed with Sam and Dean hunting down Pishtacos. She was an instant fan favorite. Her subsequent appearance in ‘Hibbing…