Bring your hand held camera from home, swap out the "family" memory card and replace it with a "work only" memory card that you keep in your desk. From there you can film your athletes' lifting technique and play it back immediately for them to see before the next set. It can be done quick, efficient, and private while also speeding up the learning process. I used it today for the first time in the High School S/C classes I teach. It also helps me as the S/C coach because I can detect technique flaw trends within the entire class, I might otherwise miss in real time. This feedback will then guide me in my planning for future workouts because of what weaknesses I see. While I haven't done it, I bet you could also use a "smart" phone to do the same thing.
So simple. I can't believe I didn't think of it until now.