I've been back at it with the gray paper lately. I've been trying out a white colored pencil for the lights instead of the white conte that I had been using. I like that I don't have to worry about it smearing and that I can sharpen it to a nice point more easily, even though it's not quite a bright as the conte.
For anyone looking for gray paper sketchbooks, as far as I know no one is making them right now. Mine is a thick stack of gray cardstock from Staples that I got wire bound at the Staples print and copy center.