Problem: The hardest part was applying 'shade' to appear balanced and good overall. I tried different colors with different shades to see what was best, took a while of try and error.
Solution: I figured that the best way to create shade is by having a black solid color over the area you want to have a shade on, and decrease-increase opacity as one sees fit.
Results: My airplane wings and back tails now have a nice shade that makes the image look better.
