Hey!
I thought it would be interesting if instructors shared exercises they think are hard. Stuff they practice on their own or practiced for a long time before playing right. Also would be great if they discussed there weak points.
Let's not go into too much theory stuff here (let's make it understandable for everyone), only specific little exercises, for examples fingerings that are really hard even for our virtuosos.
Reference to lessons (or part of lessons) are of course great.
Sorry for the bad english but you understand the point!
Gab