Here is a useful video:https://vimeo.com/ondemand/27507/1So I think you should go back to the very basics, feel your muscles and your movements, from the back and out to your fingertips, really explore what is happening and how it is happening. The professional sound is not just a job done from your knuckles to your fingertips, it may very well originate from your back and your shoulders. (Do you follow me?) There was also a course in Alexander technique in this summer school which I did not attend, but it seemed to be very interesting as well. Check that out too if you like.