Painting and drawing with the Art Media tools : Using the Art Eraser tool
 
Using the Art Eraser tool
The Art Eraser tool lets you erase art media from an image. While this tool is not strictly realistic, it does provide you with the flexibility to erase mistakes, rather than undoing entire strokes.
Art Eraser tool options
Edit workspace 
Art Eraser tool options include
Shape — defines the shape of the eraser tip
Size — defines the size of the tool head in pixels
Thickness — defines the aspect ratio of the tool head
Rotation — defines the angle of head rotation in degrees
Head tracking — controls whether the brush head bends around the path of the stroke, or whether it remains at a fixed angle