Re: Underpainting in Red
Greens in nature are usually a lot less intense than they appear--even early Spring greens. There is a lot to be said for using mostly grayed greens (with a good bit of red mixed in), then touching in a moderately high chroma greens in selected areas, then going the whole hog in only very limited areas--almost like high-lights.
I find Golden Open very transparent. Atelier Interactive is another slow-drying acrylic (substantially less slow), that has excellent pigment concentrations.
Any C&C I may make is based on the theory that even the act of disagreeing with one of my lousy suggestions may still spark an inspired idea.