Petzl has long been noted for their comprehensive information on proper use of the gear they manufacture in their catalogs and over the past decade or so in the form of videos. The newest version, found here, has some scenarios with realistic simulations. In one scene, they show a sport climbing area with a line of several belayers displaying really bad, unsafe technique (faces blurred out). It continues to astound me when going to popular climbing areas and climbing gyms how many people (1) apparently have never heard of the "hands-down" technique" and (2) believe that devices like the Petzl Grigri and Trango Cinch are "automatic belay devices". Petzl and others making assisted braking devices (the proper term) emphasize over and over that there is no such thing as a "automatic belay device".
Although the video is by Petzl, the techniques and skills apply to tube-type, plate, and assisted braking devices from all manufacturers
If you pay attention, you may note the brief appearance of a famous climber who was seriously injured by a belayer who was distracted, resulting in a communication breakdown and a very long fall.