I begin on a white canvas to sketch in the subject with Raw Umber and a little Turpentine.
I refine more if needed with the Raw Umber then add Flemish White highlights on a thin dammar layer (dammar put only under the areas to receive white). I let this dry at least two days, more if possible.
I have a lightest light represented but have more room to push darks. I establish a taste of my darkest dark and then make an educated guess at the background color and value.
I proceeded to paint the hand itself and bring the whole sketch to a finish. Obviously, most paintings don't get finished this quickly. I used an earth palette for this-no cadmiums etc.