Coffee filters are good, I have used them to clean motion picture film (another place where the cleaning material has to be lint-free) But if you want to use cotton (which is very nice) another product I use is called Webril Handi-Pads. It's pure cotton, but lint free. Works well, and on many things. You can get them online, or in some art stores, or places that supply the printing industry.
Take a look...they are really nice.
Webril Handi-Pads