Learned off people is the best way to do it.
I started learning things from my dad, and then experimenting on my own car(bad idea) from a haynes manual doing whatever I saw fit, and then went to school at UTI for about a year and learned everything I wanted to from there.
Another way I learned a lot was being a porter at a smaller car shop.
When we weren’t busy I’d talk to the techs while they worked, ask them questions about things and saw how they did stuff. I picked up a lot of things that way. Of course making sure it didn’t bother them that you poked around before hand 
Don’t get me wrong I don’t know a whole lot myself, but the most of what I do know, that’s how I got it!