(01) make the selection a shade of grey.

(02) grey scale the image, then add noise and random dark/light spots with your airbrush.

(03) motion blur the image.

(04) use the 'edge enhance' feature of psp.

(05) repeat step #04.

(06) create scratches with the line tool.

(07) create dark spots and holes with your airbrush.

(08) create seams with the line tool (optional.)

(09) add any desired rivets or screws.

(10) add additional holes and decay with your air brush and line tool.