I must actually relate a story about a huff and a rub with a hanky - not X10 related, but still worth the telling in here. Back in my early days with a DSLR, I bought a Sigma 10-20 wide angle lens [pretty sure it was under Nod's encouragement having had a look at his when we were at Silverstone one day] Anyway, a few weeks into ownership I was photographing one of our mutts paying with the hosepipe, as she does, using the 10-20 so I could get some fun wide angles. Of course, it got splashed by water, so I wiped it when finished and didn't think about it. Next time I used it i noticed circular marks on the front element. I tried a lens cloth, lens cleaning fluid, nothing would shift them. They weren't affecting images, but I was a bit gutted, permanently marking a nearly new lens. A few months later, we on a driving holiday around Norway, up a mountain with a boot full of luggage and a fantastic scene that needed to be photographed. Stuck the 10-20 on the camera and managed to put a bloody great finger smear on it in the process.... knowing my lens cloth was in the boot full of luggage and the light was changing rapidly, I asked him for his handkerchief, a quick huff and a rub with a normal pocket handkerchief and not only was the smear gone, but the funny watermark circles too
To say I was gobsmacked was an understatement, I just kept looking at it afterwards, twisting it into the light to check and check again they had really gone. I didn't even rub hard at it, just a wipe round. Not sure to this day if it was the hank, or the 'breath' that did the trick
Now whilst I wouldn't condone doing this everytime you clean, hankies are probably a bit abrasive for ongoing use, but when needs must, they won't do any harm on modern lenses