sorry more folks aren't jumping in too....its a good question in that it raises lots of potential issues and more questions!
From what you specified: that you feel the difference in when its done right vs. wrong, and that there are so many precise little things to learn.....
I'd say that is exactly what canNOT be shortcut by private lessons. It is what the body learns by doing over and over, integrating it into muscle memory, and that just plain takes time. If you just do repetitions of one tiny piece you may perfect "it" but your body will not integrate it into the larger picture and learn to generalize.
don't know if that makes sense...happy keiko..