I appreciate en value your advice but currently the thing is I really enjoy these fast skribbles. And so much more than (realistic) precisiondrawing, for me its like the difference between trying to be a good enough copier vs a free impressionist, the latter which I feel much more at home with. I do feel an ongoing improvement, as you suggest, getting more accuracy doing headshapes and developing more feel for facial proportions. As for the blending stump, I'm still finding my way with it as its hard to feel when to apply it to which area and where less or not, currently I'm trying to 'feel' the face I'm drawing instead of just copying it. In effect this means a lot of redundant lines and very fast shading and reshading with the stump but it does however feel as being on the right course, for now that is.