Drawing Tools include the Pencil, Line, Rectangle, Oval . They share a common palette through which you can change the line width, style, color, opacity, stroke style. For Rectangle and oval, you can also change the fill color.
Eraser Tool include a eraser palette to choose the eraser size.
The Pencil can also be used as a color brush. Simply increase the pencil line width in the palette.
The spray is used to scatter color on the image like that done by an air-spray. Color the selected foreground color . Place the mouse at the location where you want to spray, and press the left mouse button. the region will be sprayed with the color. The color will be scattered in a region whose size will keep on increasing with time while you keep your left mouse button down. The color will be more densely scattered near the location of the mouse and the density will decrease with distance from the mosue locaiton. You can also drag the mouse to get the affect of spraying color over a wall while moving the air-spray can.