Spotless, great post. I was wondering if anyone else besides Michael Sternbach was going to comment on their own experiences with invisibility as there are many methods.
The method your talking about is easy to follow but difficult to execute requiring a long time to get a useful effect, however the method I use brings results very quickly. In the beginning, you need 30 minutes of practice before seeing an impact when your around people and as you continue to practice it takes less and less time for the effect you get from doing 30 minutes.
You say that "the body of glass" is not a hidden method. Most ordinary people reject out of hand the idea that a person could be invisible without some kind of camouflage clothing... There are hundreds of public qi gong systems -- martial and healing systems-- yet no mention of specific invisibility techniques. What could you mean by "not hidden"? All mystical methods of invisibility can never be achieved or understood by the ordinary. And how useful any technique is depends upon a person's level and intelligence.