[Tito Champena]

Hi Leslie, I'll be glad to share with you my experience with the technique of using a monochromatic underpainting (grisaille).
I first mixed the greenish gray to paint the grisaille. This was made of Mars Black, Flake White and Chrome Green Oxide. I mixed different values by using more black for the darker color and more white for the lighter ones. After I had resolved the lights and the shadows in the painting I left it to dry for a few days.
Painting the grisaille is crucial, because you have to be sure you got the right composition and a decent drawing, since you cannot make corrections later. When painting the lights and the shadows make sure you leave the shadows at least two values lighter and the lights two values darker to make room for the glazes that will come later. I painted the dark areas of the painting with transparent glazes of dark colors and the light parts with light opaque colors. Really, there is no mystery to it, you only have to make sure that the painting has dried before you apply the next glaze. The process is rather laborious because you cannot proceed unless the painting has dried. Also, because you have to follow a plan in order to obtain a final product that is like the one you have visualized. Every glaze you apply has to have a purpose and an intended effect. There is no room for guess work.
I hope this information will help you.