I have never attended an Armorer School nor have I ever had anyone show me the ropes. After having a famous Gun Smith ruin two Revolvers I decided I'd never again send out a firearm, with the exception for something like Hot Bluing which I don't do. When I did send two firearms out to be re-blued I disassembled them, removed all the furniture and just sent the metal parts out - I was the one who refinished the wood while the metal was being re-blued and reassembled everything when the bluing was done.
I taught myself how to disassemble, diagnose, repair and reassemble the guns that interested me and that I owned. I have fabricated some parts when they were not available and did own 99% of the tools needed. I did this out of need, desire and not ever wanting to have another gun ruined or not fixed correctly. Although this might seem like I am bragging (I am not), I'd put my skills, diagnoses and repairs up against any so called Gunsmith anytime. Not saying I am a Doug Turnbull - I am not, however mechanically I have become pretty darn good. Not because I am so smart, so fantastically skilled, or what ever, just because I am not doing it as a living, I have no time restraints, I will not skimp on materials, tools or research and I am a bit OCD and very persistent.
I've been at this for 4+ decades now and only work on my own stuff. If a repair takes me 1 day or 5 weeks waiting for or having to make a part, then so be it. I am not in a rush! The job gets done correctly and up to my personal standards. I am one hell of a picky guy!
I learned and am still learning when the need arises and I absolutely love it! There are some guns I have never worked on simply because I do not own any and have no interest in. On the other hand I have worked on some very complicated guns successfully - and that gives me a great deal of satisfaction. Just to honestly disclose, I am still not a professional Gunsmith and I am not looking to become one either and I still have many things to learn. As long as I can do what is necessary to repair and fix my own stuff, I am quite content, but the learning process has taken me 40+ years and I am still learning. For someone who is interested in becoming a professional, then an Armorer's course, Guns Smithing School or apprenticeship would be the way to go. If you want a certificate hanging on your wall, again get certified. For me a certificate is meaningless.
I can tell you one thing that I know 100%....... A person who works on a certain type of gun constantly and is not always working on hundreds of different types, styles and brands is probably more adept and skilled than someone who works on every type of gun here, there and everywhere. Same think with specialty Surgeons, Mechanics, etc.
I am not telling anyone here what and how to do this, I can only state what worked for me. I do have one thing inside me that can not be bought, read, or wished for and that is the desire and passion. So as long as you are honest with yourself, know your skill and mechanical abilities, and sheer desire, you will know how to approach this What ever you wind up doing - ENJOY THE JOURNEY AND LEARNING EXPERIENCE ALONG THE WAY!