I've read a lot that if you can draw, you can draw everywhere, just because you know how to see it the right way. I think it's true, cuz look your sister did this, and I know my friend did something similar with Photoshop. He scanned one of his pieces and I told him to use pen tool and other shit so he could resize it later. I came back just 30 minutes later and he did the whole damn thing in brush mode with the same brush, just used different colors.