Thomas Eakins is one of the giants of American painting. He was born in 1844 in Philadelphia the son of a writing master and planned to study medicine before eventually training to be an artist. In Paris he studied variously under Gerome and Bonnat before returning to Philadelphia where he was to live and work for much of his life.
He taught in the Pennsylvania Academy of Art. For centuries artist had learnt to draw by firstly working from engravings, then classical statuary before finally being allowed to work from the live model. By contrast Eakins encouraged students to work from life straight away and to also sketch freely using a brush. The following passage contain’s Eakin’s explanation for thisand is taken from an interview with the artist in Scribner’s Illustrated Monthly Magazine from 1879 entitled “The Art Schools of Philadelphia”. It’s an interesting passage, although from what I know of Eakins he was a very meticulous worker and not at all “loose” which is the approach he seems to be recommending here.

“The brush is a more powerful and rapid tool than the point or stump. Very often, practically, before the student has had time to get his broadest masses of light and shade with either of these, he has forgotten what he is after. Charcoal would do better, but it is clumsy and rubs too easily for the student’s work. Still the main thing that the brush secures is the instant grasp of the grand construction of a figure. There are no lines in nature, as was found out long before Fortuny exhibited his detestation of them; there are only form and color. The least important, the most changeable,the most difficult thing to catch about a figure is the outline. The student drawing the outline of that model with a point is confused and lost if the model moves a.hair’s breadth; already the whole outline has been changed, and you notice how often he has
had to rub out and correct; meantime he will get discouraged and disgusted long before he has made any sort of portrait of the man. Moreover, the outline is not the man; the grand construction is. Once that is got, the details follow naturally. And as the tendency of·the point or stumpis, I think, to reverse this order, I prefer the brush. I don’t at all share the old fear that the beauties of color will intoxicate the pupil and cause him to neglect the form. I; have never known anything of that kind to happen unless student fancied he had mastered drawing before he began to paint . . .
The first things to attend to in painting the model are the movement and the general color. The figure must balance, appear solid and of the right weight. The movement once understood, every detail of the action will be an integral part of the main continuous action; and every detail of color auxiliary to the main system of light and shade . . . To these ends, I haven’t the slightest hesitation in calling the brush and an immediate use of it, the best possible means.”