What's the best way to get dust off a piece of filter? Or should I just toss it?

BTW if you ever need to get dusts off your enlarger condensors I've discovered a very simple method. Just insert a piece of filter that's got a static charge between them. Suddenly all the dust that you didn't know had managed to get onto the condensors is all over the filter. Well at least the condensors are clean now. Lucky I'd cleaned them the day before.