When I'm out painting on location I sketch my view in a soft wash of oil paint...followed up by re-approximating my placements of man made objects. Meanwhile I try to capture the clouds with a few quick bush strokes. These days I use a small digital camera to photo the sky and the scene so that I can continue on with my painting...not fearing a rain storm...nor the swift and total change of the feel of the sky that occurs these days of global warming!