Hi, I am a full-time piano tuner !
I live in Belgium, where there are no schools for piano-tuners neither.
So five years ago -- at the time I was doing water analyses in a lab, and wanted to change -- I read an advert from a piano company. They just asked if I had some (basic) knowledge of music, and if I was really motivated to learn the job. They would let me try a couple of times, to evaluate how I would be getting on with it. One of their tuners showed me how to do it (with a machine), and then watched me trying to tune a part of a piano. In the beginning, it's not easy at all; you really have to learn how to manipulate those tuning pins; it takes 3 or 4 hours to get a piano finished, and the results of these first tuning attempts are never brilliant. But my future collegue thought my bungling wasn't that bad for a beginning, and I was accepted. I had a 6 month training in the shop's workplace: besides much tuning practice, I learned also how to do some maintenance and repair works, like replacing broken strings, bimsing hammer felt, regulation, voicing, ...