No offense at all intended toward the union folks, but staring out as the grunt for a knowledgable small shop owner / senior j-man is an awesome way to get an understanding.
There's less exposure to mutiple instructors, so if your foreman's got bad habits, odds are you'll pick 'em up, but is he knows his rear from a hole in the ground you'll get a great "one on one" learning experience.
And, much as I hate to bang the old guy drum, starting out at the bottom lugging supplies and tools out of the van helps you learn what...
Making holes, nailing boxes, and strappng pipes helps you learn where...
Measuring, cutting, threading & bending helps you learn how...
Listening helps you learn why.
Good luck in the field!
