The cotton ends of QTips are very abrasive. Metal parts exposed to moving cotton/cotton dust in cotton gins are made from abrasion-resistant steel, and it even chews that stuff up after a while.
I use paper towels to blot.
I should have said, as mentioned above, a good "blowing out" with a can of compressed air, and a gentle brushing with a natural-hair camera brush is my first step.
If you wash your hands thoroughly, and keep your nails off the glass, the skin of your fingertips won't damage the lens or coating....and it's easy to get into corners.
Once you've cleaned the lens with the soap solution, rinse with cold water.
Mike