Use a non paper type dry lens cleaner such as a lens pen, or micro fiber cloth type lens cleaner with no cleaning solutions added.Lightly Use a clean dry lens brush first before using the dry padded lens pen or micro fiber cloth. I have used these to clean both the brass and plastic on my lens collection. These also work very well on the reunion and NY city skyline acrylic pieces. I would not use liquids of any kind on the lenses as it may compromise the laguer finish on the brass work and could also effect color in the plastic. Liquid also can coagulate particles already present that can scratch the plastic and metal.