Hmmm...use lime white "at the end of the underpainting (verdaccio)." And then don't use it again until the painting day is almost over? So you build up the main forms at first, using verdaccio and lime white, like a monochrome picture? Then start applying the many layers of colors for the full value painting? Then finally use some lime-white tints and accents to finish?
It's starting to sink in,...I think. In any case, I'm going to try painting something soon , using the Florentine putty. But instead of mixing the whole bucket of putty with sand, I think I should save about half of it, in case I want a different mixture. Plus, an amount set aside just for lime-white.
Your advice is a great help Ilia, thanks. We'll see if I can follow it all the way through.