I zoomed in on the image, 4:1 ratio, as this is almost pixel by pixel work. I ended up using the 5 x 5 fuzzy brush that came with the GIMP tarball. As usual, your choice depends on the resolution of your image. A fuzzy brush is highly recommended. On this web sized image, the 3 x 3 fuzzy brush didn't work fast enough. As always, you can Edit -> Undo until you make the right selections.