I've done two more weekend classes. The first was "Structure and Form", with the first day concentrating on the bone structure of the human form, and the second looking at drawing from life, partly using the lessons from the first day and partly using a more gestural style.
Sarah also gave a demonstration of a glazing technique, where the tones are established with a Burnt Sienna underpainting, then the colours were built up with various glazes of transparent colour. It was fascinating to watch, and definitely something I'll have to try.
I had always understood that there are varying degrees of transparency with different pigments, but this class gave me some understanding of how to make use of the transparency or opacity, and how to choose which pigments to use for various effects.
Also good to see the difference between zinc white and titanium white, with zinc white being much better for lightening colours without dulling them down as happens when mixing with titanium white. I will definitely be using zinc white for most of my mixing from now on.