When I first started teaching guitar nearly fifty years ago I used a normal method book (series of books actually) that my students would purchase from a music store. No surprise there. That's pretty much how everyone does it. After doing this for a couple of years I noticed that I always needed to make some adjustments in the method. And some books had certain details just plain wrong.
Over a period of years I bounced from one method to another in search of the "perfect" system. Of course I never found it, so I started writing supplement materials. In time that process developed into writing my own method. To be honest it wasn't a very good method but it seemed to work for me. Other teachers tried it though with less than desirable results. Perhaps the best part of it was the "primer" for very young children. I'm still proud of that little book.
It has been a very interesting experience to self-publish. I've worn out a couple of copiers. I own an inexpensive binding machine. And I buy paper by the case. It takes a lot of time to make books - even little ones and there isn't hardly any profit. The upside is that I get pretty good results.
The process has changed over the years. When I first started I would draw each note by hand with a fine tip pen and a ruler. It could take me all morning to do one page. When all of the music was finally written I would type (yes on a Remington typewriter) all of the directions and explanations. Then with scissors and rubber cement I would cut out each part and paste them in the proper order to make a book. I know......I sound like I grew up across the street from Fred Flintstone and Barney Rubble.
Modern technology has been very useful. Today, of course, to cut and paste is simply a couple of keystrokes on the computer. My music writing software turns hours of writing into minutes. And a mistake is no longer a reason to despair. And I don't need 6-8 square feet of workspace to do the layout.
Most importantly it gets me out of the publishing business. Everything is in the computer so I can fix any mistakes or change the order of things if I need to. With my online students I now include the lesson materials for free. I just email the necessary pages and accompanying recordings if needed. I also have some free materials on my website with more to come. All of this makes my job easier and the process far more efficient. My hope is that it gives the impression that I'm a better teacher than the next guy.
The information needed to learn the guitar hasn't changed very much. Each teacher has his/her own way of explaining things. But computers and the internet has had a huge impact on the process just like nearly every other profession. I'm constantly looking for a better way. Bob Dylan once said, "He who isn't busy living is busy dying." For me, teaching is living.