The first skill that I can think of is observation skills. Artists can be observing current events, psychological issues, nature, and virtually anything to get great inspirations, and I feel observation is an essential starting point for any artists. What artists observed in their lives are often embedded into their art work, and the observed elements can add more meanings to the art work. Through a piece of art, artists can express their unique ways of thinking and gain the ability to tell stories visually.
I do not know if this is a skill, but having a determination to achieve one’s best could be very important as well. As Sally Mann showed her work ethic in her video, she has the determination to find the image she wants, and her family even describes it as “intense.” She can have stacks and stacks of pictures, but she would not quit until she gets exactly what she wants. After all, I believe any skills can be learned if the person truly commits to something. So the amount of passion and self-discipline Sally Mann showed could be more important than any skills for creating art.