Erik - I am a but overwhelmed. That is .. comprehensive!
I am about to get deep ended in a welding adventure involving heated cast iron. The most history and technique information I get is from Wikipedia and YouTube, and asking on HM. Then I find the discarded brake caliper, or any cast iron, and have a practice attempt on a small piece. Then go for the real thing!
Of course, folk get trained and qualified in welding, and build careers of practical experience. I have to get somewhere with it, done any other way I can. It may end up hilarious!