You misunderstand - perhaps I was not clear enough. The "no's" were not saying don't do those things, but rather that they were not the way I learned the most. By all means get your hands dirty. In the mechanic's course I created students worked on bikes that our co-op then sold or rented, not on nice clean new equipment. Building from scratch wastes a lot of time on things one will do infrequently and on compatibility issues that don't apply to many circumstances. I don't believe trial and error is a good description of the best approach, as there are far more ways to do something wrong than right. I acknowledge that bicycles are not exceedingly complex, but I have seen many people make errors due to tunnel vision.