100% cotton did not help me too much, many mishaps but I will post it anyway to show I tried. I couldn't get colors mixed right, everything turned green, however I have seen the "green flash" when sun sets sooo... Clouds turned into caterpillars (need one of those tools for masking). I finally just tried to fix them with paynes grey........ Still unsuccessful with scumbling. I had to paint the sun as also could not get any softness - maybe I should put white gouache on it? Anyway was a good try..