MRC You've said your teacher was disappointed at the amount of progress you made with 6 hours of practice on a piece. The first vital question is this: 6 hours solid, or 6 hours spread over the week?
It is about an hour a day, for 5-6 days.
He did talk about how to practice. I just find it hard to implement his advice outside of a lesson because it is so cognitively demanding. He had me practice in specific ways during the lesson and timed me. He asked me to first read the right hand of two measures, then the left hand, slightly under tempo, with the correct hand movements until I got it correct three times in a row, each. Then, to play the entire thing slowly and correctly 3 times in a row. I could play the two measures (of a very difficult piece) after 12 minutes.
Then, he said you would repeat that method for 1.5-2 hours, and that you would solidly learn 8 measures. And so within a week, that would add up to say 40 measures (or at the very least a page) played at a very good level. It makes perfect sense, but I find it very hard to do this. I felt like I was dying after those 12 minutes because it required so much concentration. The fact that I could pull it off during a lesson means it's possible though, so I'm getting very frustrated with myself.