If Flyers or any other CFI program isn't an option for him, then may I suggest that he actually get out and immerse himself in a teaching environment to break his shyness? There are many volunteer teaching programs within communities that are constantly seeking out volunteers to teach basic English, math and so forth. One of my personal projects to see whether I had any capacity for teaching was to sign up for a GED prep course for older students. It was one of the best things that I could have done, gave me a boatload of motivation to tackle CFI coursework at a time that I had zero, and may serve him well in convincing his examiner or potential first employer to favor/hire him if he has some previous teaching experience.

Another thing that he could do is to sit in during his mother's classes if she doesn't have any constraints in permitting that. Observe how she teaches, what techniques she employs and how her body-language and demeanor strongly affect student reactions.

I agree that giving up is not the answer. Anyone can teach if they want to do so strongly enough, but first they must believe that they can do so, and that's where it all starts even from the first time that someone climbs into an airplane to learn to fly.