In an interview Andrew Wyeth said to Thomas Hoving: I work in drybrush when my emotion gets deep enough into a subject. So I paint with a smaller brush, dip it into color, splay the brush and bristles, squeeze out a good deal of the moisture and color with my fingers so there is only a very small amount of paint left. Then when I stroke the paper with the dried brush, it will make various distinct strokes at once, and I start to develop the forms of whatever object it is until they start to have real body…. Drybrush is layer upon layer. It is what you call a definite weaving process. You weave the layers of dry brush over and within the broad washes of watercolor. Andrew Wyeth’s curator Mary Landa has told that in some situations he use a special prepared brush with a tip which consists of down to one sable hair. (http://www.petervnielsen.dk/Drybrush_Andrew_Wyeth.shtml)