Here are some progress photos of a piece I did this past August. It's approximately 22x36, oil on canvas, titled "Red".
After I did a few sketches to decide on a composition and a quick color study, I did an umber underpainting to decide on my values and then blocked in color.
I continued working all over, never stopping at just one spot, so I could always compare values and intensity of hues. I also check the drawing every day, since it is a live model, it is important to be flexible and change the drawing if necessary.
Every new day I sit in front of my painting, even if I've been working on it for weeks, I pause and sit quietly for 10 minutes, assessing what I see/drawing/values, etc. I might make notes so I remember throughout the day. I am always surprised, thinking "Why didn't I see this yesterday?".
"To see we must forget the name of the thing we are looking at."