Some of the best Shotgun Shooters in the World shoot with the Magic Dot.
If he's never shot ANY LONG GUN at all, I'd try the left-handed routine. If he has experience with rifles off of the right shoulder, go with the dot.
The Dot has to be put on the lens (shooting glasses) by someone with the experience to do so. And even then, I have had Master Class buddies "peek" around the dot.
Both eyes open and use the Dot!
