Kikkan Randall isn’t particularly professorial, what with her pink hair and her affable demeanor. But since arriving back in the U.S. last week, fresh off the World Cup circuit in Europe, Randall (APU/USST) has been teaching lessons, all right, with the trails of Sun Valley as her classroom, and the North American women’s field as her pupils. After Sunday’s unit on distance classic skiing, Tuesday’s session was on how to ski a skate prologue. In...