Well, I thought I was close to finished with this painting until I started painting hands. I spent two hours on just the hands today and it was well worth it.
One of the hardest thing about painting a figure is giving the body a since of structure. I want the viewer to be able to tell that there is skin stretched over a complex weave of bone, muscle, veins and tendons. To achieve this I focus on the very minute little changes in value over the form that indicated structures beneath the skin. Some color changes go into this also. If skin is stretched over a vein you will see a tinge of green there, plus a shadow and light side. If the skin is stretched tight over bone, like for the knuckles, elbows, clavicle and knee you will see a much lighter color, close to white in some instances, or pink. Of course all of these observation are based on light skin tones.
Above all it is just about looking and seeing exactly what is there. Never make anything up or randomly put a stroke on the canvas when in the finishing stage of a painting. I’m constantly thinking about drawing, value, and color when I put a stoke down. In that order also.