"If you don't mind me asking, what is your expertise from which you know all these different techniques?"
Just found this question while searching for info on sheet metal lugs...
The basic thing is a 30 year fascination with making stuff myself. I started with stained glass, fly tying, woodwork, boat building, boat design... It just keeps building. Some of these things have been dropped along the way, some I only did to save money and don't care about, like making my own sails. Just keep buying the tools, paying for the cost of my own shop, and keep slugging away at learning new techniques. Some stuff I am really good at, been doing it 30 years and it's there, other stuff is a struggle. Making bikes has been hard because to do it independantly is pretty expensive. Frame prep tools!! Torches!! I have a plan to get some money out, but I don't count on it.
Some of the activities are complimentary, like layout and design, but some of it is not. I may have picked up a new craft every year for thirty years. It takes longer than a year to do it, but over thirty years you can pick up a lot of stuff. If UBI can teach someone the basics of doing a frame in a few weeks, then think of how much stuff you can teach yourself in 30 years if your interest didn't flag, and you had the money.
Overall I wouldn't recomend it. I valued the idea of being widely skilled when I was a kid, the Renaissance idea. But society doesn't value this idea, not really. And it is getting worse as time goes on. The newest thing I have observed is the decline of materials. With stuff coming from china, and being sucked back there, it is sometimes hard to find local stuff, and more to the point it is rare for the home made stuff to be cheaper these days. At some point, even for pleasure, there are things one doesn't bother to do for oneself. It hasn't got that bad yet, but the trend line is there.