Below are links to oil painting class demonstrations from the Art Students League a very old and apparently still a traditional art school. What you are being taught are two different approaches closely tied together that evolved from late 19thC representational art. Just about everybody in art books from about Manet to Franz Kline learned to paint this way. And that includes both de Koonings, Gorky, on up to Diebenkorn, and the SF, LA west coast schools through most of the 1950s.
I got a pretty bad version, mainly because there were very few traditional painters or at least painters who went through this regime by the time I got into school ... so they couldn't teach it. Also for some reason teachers were very reluctant to work in studio with students. They walked around and made comments. The only exception was Hans Burkhardt who had no apology for grapping a brush, mixing a few colors on your palette and overpainting on your work. Most students didn't like this at all. I was one of the few who didn't mind. Usually the work was going bad anyway. On reflection, years later I see what he was doing, which was readjusting the main blocks of form and re-keying the color fields. I tended to use pretty colors and Burkhardt would be attracted to these patches and immediately muddy them out.
These videos are clearly master classes, one time demos that probably don't reflect their everyday teaching. It is very risky to paint in class in front of students. Things can go bad in a hurry. But in fact it is equally risky to paint as a student in such a class. It's something everybody has to get used to.
http://www.youtube.com/watch?v=AMeb2ptOrw0&feature=relmfu
http://www.youtube.com/watch?feature=endscreen&v=VtgIxYerI2s&NR=1
What these videos don't show is how much of what you are watching depends on their drawing skills. The key thing to notice is that they start by blocking in masses and implied movement, and roughly measure in proportions. The general method is to gauge the size of the head in relation to the canvas and use that as the measure of the rest of the blocks of the torso, arms and legs. The general proporition is 7:1, about seven measures of the head to the standing figure (see di Vinci's famous drawing). Children of various ages have different proportions so its a mistake to paint them the same, because you end up with that little people look. Play with your eyes to see this in people around you.
So comments prefaced with the fact I certainly could not achieve the same results...but they are where I would want to be, when I want to go there.
Gregg Kreutz' model is more heavy set than his rendering, most particularly with the head and neck, which is followed through in her upper torso. He's certainly right about the beauty of her posed head which gives her some great character. Her embroidered silk blouse is practically out of a french studio circa 1870s on up to Sargent. This technique and style evolved as a reaction to the overly refined neoclassicism of academy painting of Ingre and David. It became an academy of its own and was routinely abandoned until it nearly disappeared by 1960, just when I started.
Sharon Sprung's back which is about the most difficult pose there is, is a little too flat---although there are reasons to keep it that way, meaning the integrity of the picture plane or unity of the figure and ground. Her figure gets much more dynamic in the head detail which is at a deep complex angle to the picture plane.
It's worth clicking on the box that links to her webpage. She represents the high end of the photorealists. I like her cityscapes more than her figures and still lifes.
Here is another variation on near photorealism that gets way beyond it in a particular way that reaches back into Antonioni (in his best). The extraordinary vacuum of the real. Vijia Clemins. I saw her work back in the late 60s or early 70s on a trip to LA and she knocked me out.
http://www.pbs.org/art21/artists/vija-celmins
CG