Blow with compressed air and Lens Pen when I need it. Lens Pen has been far superior to any "wet" cleaner I have acquaintance with. FWIW, the optical repair department at Captain's Nautical Supply tested the various fluids and used to say that plain old Windex was as good and safe as anything that can be used on coated lenses. I haven't kept up with the discussions on the bird forums regarding what the contemporary thoughts are, once I began using Lens Pens I haven't found any need.