Well on Surefire's coatings, you can scratch it by simply touching it. I heard Carley's coatings are tougher, but by how much? Can you say, clean it with your shirt and not scratch it?
Not recommended, but I have used the cloths used to clean eyeglasses with good success.
I usually use diluted dishwashing detergent, let it sit for a minute or two, rinse with distilled water, and blow dry with canned compressed air. If that doesn't work, I GENTLY rub with one of those super soft cloths and use the same process.
DO NOT touch the surface of a Carley reflector with ANYTHING, if you can help it. If you must do so, don't rub, but rather pat the surface, and do as bwaites says and use one of those mirco fiber cloths for AR coated glasses.