1: You could buy a really expensive cleaner for it. :(
2: Good old soapy water will do it, but be sure to dry it, and oil it up with a thin oil to trap the dust. :D
3: Final straw is use parafin or petrol, but be sure it is clear before replacing it. :?
I have always favoured soapy water, as it doesnt damage you or the environment. But as i said, allow it a good few hours on the washing line, and oil it with thin oil as it traps all the fine stuff on the outside.
