[popo]

I do use a lens pen sometimes. On one end is a brush, the other end is a soft pad which gets coated in a fine dark powder. Whatever it is, I think the idea is the powder will soak up any grease. It doesn't leave any noticeable residue on the glass. There is a sponge with more stuff on it in the cap which re-coats the pad between uses. I find this overall hand to use for pot cleaning.



Beyond that, I do use the disposable Pec Pads with cleaning fluid.



In the field if I have neither of these I'd just try and find a clean bit of clothing or anything else to had for a quick wipe. Usually it's got to get pretty bad before I do that, like if I have mud on the lens.