Just finished watching Mark's Part 3 on Painting Realism. I think I'll have to watch it another time or two to understand everything.
He seems to be putting in two or three layers to bring up the highlights and color. In the bottle, he painted the bottle the more neutral underlying color and then came back and brought up the green in it. In the box, on the carving, he also did that in several layers.
very interesting! I really like his careful, methodical approach! Looks like it take a light touch with the brush, though.