During my holiday I worked through the book by Carl Purcell "artist brain", did some exercises and tried to incorporate the ideas into my normal sketches. I found that my problem with Purcell's method is that it makes the paintings far better, but he feels very free towards the subject he draws. Very often the painting is a very far cry from the original idea, even so far that you wonder why he bothered to check reality in the first place. So I looked for subjects where the required values were present. And that proved to be very difficult.
Still a long way to go.
This watercolour is one of the exercises I did based on the book.