I found that placing a light jumpstretch band around the athletes knees is a great way to get them to both externally rotate and initiate the knees back. Place a band around the knees of the athlete and stand in front of them pulling the band gently towards you. The athlete should be deadlifting something light like a kettlebell (a barbell will run into the band on the way up). Pulling the band forward and in will cause the athlete to push their knees back and out to resist the band. It’s a great two-for-one.