teaching someone how to be a technician is like teaching someone to be an artist.
you can be taught to draw a circle or a line but we would never want to see your stuff on display at an art show.
They can teach you the basics of an engine but not give you the mechanical aptitude to diagnose issues real time. Many good techs can diagnose an engine before even before starting it and hearing it run.
I've got certifications from many of the larger small engine manufacturing companies (briggs MST, kohler, Stihl, etc) and they are pretty much about as handy as damp toilet paper.
I learned the ropes as lakesuperior said, i started by pushing a broom and cleaning air filters.