I spent a good portion of yesterday using my portrait photography retouching skills to retouch an image for a skin that I am working on for a plane that is still a work in progress. The techniques I used to remove pimples, scars, braces, glare on eye glasses, fly away hair, lint on jackets and dresses, were all put to good use fixing a photo of a painting on the side of a fairly historically significant aircraft. The finished product isn't perfect, but it is close enough for government work. Unless you have been to a museum in Italy (can't remember the name of it) and seen the plane this painting is on, you would never know that some areas of the painting just aren't right.
Here are two screenshots, one of the original photo of the painting, and one of the post-retouch work.