Recently I went searching for information on the grisaille painting technique of laying down a monochromatic underpainting. There seemed to me to be surprisingly little information around. Actually there seems to be very little information about painting in general, but that's another story. I finally found a technical video rental company which had in stock a DVD of a demonstration, by Johnnie Liliedahl, showing the grisaille technique, using Waterhouse's "The Lady of Shalott". The material is comprised of two discs and some text material. Interestingly it is mentioned in the text that oil paint becomes translucent in time, regardless of how thickly it is applied.
I have yet to view the entire demonstration, but so far it is very well done.