Tito,
Michael Georges, a member of the Forum, studied under Frank Covino, who teaches the glazing technique or the Grisalle method. Frank has a web site and you can order his book from the site. It is very informative, and I refer to it often.
The title of the book is "Controlled Painting". I believe it is out of print, but you can get a photo copy of it. Unfortunately it is not in color, but it is very detailed. The web address is
www.portrait-art.com.
He also discusses glazing in great detail and Verdaccio, a toned greenish underpainting using nine shades of paint mixed with white, ivory black, and terre verte.
Hope this helps.