Well.... so this is just my opinion....
Most trades are about 75% experience of doing, and 25% knowledge learned.
Meaning, you'll get far more, and learn faster, if you can join an apprenticeship.
I went to a school for a trade, and I was consistently 100% top student A+, never missed a single question on a single test.
I also was the absolute worst student in the class at actually doing the work. No skill whatsoever at doing the job, but I knew the answer to every question, and knew everything there was to know about the trade.
Trades are better learned by doing it, rather than head knowledge. Now if you already are pretty handy at pipe-fitting, and you are just looking for that best practices, then scout around for local state colleges. There are usually some with trade classes. Teaching you best practices, and building codes, is very important, and obviously useful to learn.
But if you actually want a ground up learning a trade, I believe most state pipe-fitting unions, have apprenticeship programs. Here in Ohio, I see them being advertised pretty regularly. Of course it means you have to spend a year or two working as some guys pet... and some guys are better at training people than others.... but that's honestly the best way to go in my opinion.
