Dear Clive,
Welcome!
As you begin this course of inquiry, I would recommend you search the Forum database for the rich resources presently here. You can do this just by clicking the "Search Messages" link at the top.
For example, go here
http://forum.portraitartist.com/sear...der=descending to see the search results for grisaille, and here
http://forum.portraitartist.com/sear...der=descending for verdaccio.
Best wishes!