In graduate school I needed a lot of metal work done for my physics research project. The experimental machine shop was way backlogged so I went down to the basement and told the head of the shop force I'd be willing to do any work he needed if he would train me on the lathe and the milling machines (the main shop was off limits to anyone not employed as part of the shop force).
The deal we struck was I cleaned up the shop every evening (swept the floor, cleaned all the machines, re-stocked metal where necessary, etc.). When I was close to being finished I'd give him a call at home and he would come back in and we would start my next lesson. Basically, I became an apprentice. I made all of the metal components for my experimental apparatus and at the end John said he was very impressed with what I had done (so was I ). That training helped me land my first job as a research physicist in industry and it has stood me in good stead in many other ways over the years.