The Bucket Fill
tool can be used to fill in parts of an image, (gradient) shade, and dither shade.
This can be used to fill in areas of in image, by putting the cursor over the part, and clicking.
The Shaded Fill
tool can be used to shade parts of an image, by clicking and dragging with the tool selected.
Dither Shade FillEdit
The Dither Fill
tool can be used to fill images with a dither. It is used by clicking and dragging across a part of an image.