Scuff them up with some real fine sand paper like they use to water sand cars with...then paint them and clearcoat them. You can get a cheap air brush at Harbor Freight. When you get your paint be sure to get some thinner as you will have to thin it down to use with the air brush. Just play around with it...practice on some tin cans or something. And the good thing is...the fish don't know and don't care if you did a real good job or not.