Once the brightness and contrast was cranked up in Photoshop, much of the unwanted lines and grey vanished. Much of it, but not all. I had to paint out every spot, or fuzzy grey area that was left, using the Paint Tool. But at last I had a firm enough figure to start colouring. First step, though was erase the background entirely. Second, fill the background with a light grey, to make it easier, later, to isolate Saara's figure in the upper layer, and erase the rest.