Actually, using a cotton cloth to clean a lens is OK...as long as it's 100% cotton. Nothing else is good. The best, in my opinion, is those micro fibre clothes. The really soft ones are the ones to use. Nikon also makes a lens cloth that's on a key fob kind of holder.
I keep a 1 Gallon Ziplock bag in my gadget bag at all times. During the hot (91 degrees +!), high humidity and inside a/c usually under 80, it is nearly impossible to avoid fogging.
The 1 gallon Ziplock fits my D70 perfectly.
How-ever, remember to use a drinking straw and BLOW UP THE BAG! This gives a thermal cushion between the outside heat and the cooler air inside the bag.
Yes. I know it sounds weird, but what you are doing is creating a sort of thermal buffer zone. The air in the bag has to heat up to the same temp as the outside air.
The camera is protected from the heat and humidity by the buffer zone. As the air inside the bag heats, the camera is also heating slowly.
Kidding aside, isnt it harmful to the lens coatings when you rub something on them ? I just use a rocket blower to blow off dust on my lens, and on occasions that the lens comes in contact with fingers, i just use a lens pen to take out the finger prints.