The King in ArtStudioPro!
I spent HOURS upon hours sitting in my car so here is one of my doodles while doing so. I recently posted about some of my favorite apps on my iPad so here is an example of something I did entirely in Art Studio Pro. With the exception of the "smear" in the background, I only used the HB pencil with the tilt function. I erased nothing and just kept added right over my scribbles that started it.