If you have an air compressor blast it off with an air hose and then give it all a good wipe by hand. I use to be meticulous about it cleaning the entire bike and the inside of my fairings perfectly every time I had them off. The truth is, if you can't see it when the bikes all put together there's no point in stressing about keeping it spotless. It's good practice I think, if you take a part off, clean it reasonably well before re-installing it but no need to go overboard. It'll just get dusty and dirty again and no one will ever see it. That's my take anyway. 
