The first one was my entertainment on a recent cross-country flight. I knew the motion of the plane would prevent precision, so I planned on the wobbliness of the vertical lines giving it a bit more texture.
Back on solid ground, I did the second one, which required a steadier hand. At one spot, I goofed and used the same color adjacent to itself. A little cutting-and-pasting plus a little Photoshopping hid it pretty well, I think.