Please accept my apologies, I wanted a catchy title that people may actually read, I thought go down the sex angle as most people are a bit saucy, but this isn't about polishing helmets, it is related. Does anyone have any tricks to cleaning the white plastic issue cap covers? I have a mark on mine that just wont go away. I am not able to get to stores from where I am before I have to wear it. Any advice would be much appreciated.