Not sure if you should try this at home though it worked for Mathieu Stern as you can see in the video below.
What is it about? Instead of using a lens cleaning pen, you can do the same job with a candle, a spoon and a microfibre cleaning cloth. The tip of a lens cleaning pen is covered by “carbon cleaning compound”, which basically is soot. Soot sticks to oils and fats and hence works perfectly with those fingerprints on your precious lens. What is shown in the video is how to make your own “carbon cleaning compound”.
Watch the short video below carefully before trying it. Be aware that soot is a gentle abrasive, but still an abrasive. Using this trick too often might damage the lens over time (though it seems to work fine for Mathieu Stern).[via DIY Photography]