A Candid Portrait Sketch - final piece

This is as far as I will go on this candid shot and I was trying to understand some further steps into the cross-hatching of values after having tried to capture the planes correctly. Then I discovered the paper I was drawing on was not helping me but hindering my attempts to lay down dark values and this created a new problem of me not understanding value compression. Techniques that I discovered I need to practice are my cross-hatching proficiency, how to get value compression, how to keep my values simple and to keep them to a limited number. 

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Perhaps there are many more things for me to discover and it will be good to get some of the physical difficulties figured out. I will only be able to blame the paper this one last time but I think I caught the candid moment somewhat so will move on to my next lessons to learn and try a new unsuspecting stranger.
Most of the time my efforts with portraiture will be with oils but I have found I like drawing with nice sharp pencils. I have started sharpening them to a nice long spear shaped lead end. Another thing that will take some practice to perfect.