I let the under-painting dry for a week until it was very dry to the touch. (The paint layer is very thin, so I probably could have painted over it in 4 or 5 days.) I was eager to see how my idea of under-painting the green cloth in yellow would work out, so my first step was putting down a thin glaze of cadmium yellow over the cloth. This is all I did for my first session, because I want to put down a green glaze over the yellow area as soon as it is dry, in 4 or 5 days. If I had started to paint the rest of the canvas, those thicker layers, by contrast,  wouldn’t be dry for weeks. They would inevitably smear as I worked with my green glaze. So, it was a short session today!