Clive: As to how to proceed with a painting using this technique, here (in general) is how I have painted using this method in the past.
The method was taught to me by Frank Covino, an excellent teacher.
The Cartoon
Covino uses a graphing system to get students to draw their forms to the board in charcoal - no graphite - graphite is slick, can leach through the paint, and is not recommended for drawing anything below a painted surface. Next, you do a complete charcoal rendering of your form on the board - establishing your complete value system and taking the cartoon to as much detail as you can. When complete, you spray the board with Damar Retouch Varnish to seal the charcoal a little and make the surface ready to receive your underpainting.
The Underpainting
Covino recommends the Verdaccio method for underpainting flesh. He also does the rub out method and grisalle, but only for advanced students. Covino's palette is a controlled palette based on nine values from dark to light. Thereby, he has you create nine values of Verdaccio using Flake White and Chromium Oxide Green (I have tubed these so I don't have to remix every time). He recommends mixing the verdaccio with 1/5th Liquin - again because of short workshop time and also because liquin dries rock hard permanent. You proceed with the underpainting by simply matching the values that you see in charcoal - if you rendered a cheek in value 7 in charcoal, then you simply paint over that cheek with value 7 verdaccio. Again, you do the underpainting to as fine a detail as you can as your underpainting will actually serve to define the form for some parts of your painting that you will glaze.
Color Stage
With the Verdaccio complete, Covino recommends beginning the color stage by glazing first and then applying opaque paint. Most backgrounds can be accomplished with one or more glazes over the detailed verdaccio underpainting. Covino's medium makes his glazing technique work - most mediums today are not suited to glazing. The medium is comprised of:
Damar Varnish
Stand Oil
Venice Turpentine
Rectified Turpentine
Once the glazes are completed, then you can go on applying more opaque paint to the areas of the painting that require it. He recommends "scrubbing your darks" and "painting your lights". The lighter the paint, the more heavily it is applied. He never recommends applying opaque paint over a fully dried glaze BTW. For flesh (no glaze on flesh - opaque only), he has a specific pallette that is mixed in several stages. First, you mix a row of nine value neutral grays, and to them, you add the color of the light (i.e., Zinc Yellow). You then mix a row of nine value oranges. By mixing the grays with the oranges, you get nine values of flesh tones. Some of the gray is saved out to gray certain areas like edges, etc. He also has you mix a row of blood tones. The blood tones are never used straight, but are mixed with some of the flesh tone of the same value to create a redder tone of flesh that is added to cheeks, tips of fingers, nose, etc. Again, you are just matching value to value between flesh and verdaccio. Put a value 4 flesh over a value 4 verdaccio. He recommends painting into a wet surface by lightly spraying medium over the area before you begin applying color. When the painting is done, he recommends one coat of medium over the entire thing (when dry enough as to not disturb the surface) to give it a uniform gloss. And of course, varnishing the painting with Damar Varnish after 8-12 months.
Summary
So that in a very small nutshell is a quick sketch of Mr. Covino's method. If any of you have an opportunity to meet him or take a class from him - let me plug his talent, his knowledge, and his ability. He is a master of our time (my opinion). He also admits that this is just "one" way of painting. When you consider that he is largely teaching an untrained pupil-base, the method is very effective and people who have never painted before in their lives come out of class with some pretty impressive first paintings. For the intermediate or professional artist, the value cannot be over expressed - RUN don't walk and get into a class, and get his book "Controlled Painting". Frank's website is
www.portrait-art.com. The site is NOT impressive, but his work is.
Frank's method is a great place to "start" for anyone who is serious about making a real go at painting realistically. There is so much info, techniques, etc. that you could use his teachings as a very solid base to begin your own explorations from.
I have since modified many of the things I learned from Frank into a system that works well for me. I don't use his medium anymore as I have found better for my process. I am now exploring a direct method of more dead color underpainting I learned from William Whitaker - another Master painter of our time.