I think there was a brief discussion here about the Flemish method of painting and grissaile in general and one of the topics on last week's Empty Easel site is about the Flemish method. Below is a link to the first post on the method and the author also tells and shows how she prepares a board for the painting. You can join Empty Easel and get an email about each week's topics so you won't miss out on any of the instructions.
http://emptyeasel.com/2014/12/02/how-to-paint-using-the-flemish-method/
It sounds very complicated but the results are really astounding.