Just wanted to tell you that, after lots of experiments with (cheap) methanol, Q-Tips up to expensive sensor swabs with "Eclipse" I finally found "my" solution :-).
It' cheap (20 Euro for up to 100 cleanings), easy and VERY effective! It's called Sensor Film (and no, I am not related to that guy in any way :-))
Check it out at
www.sensor-film.com/