Nothing is "the" safest if you try to clean the headlight reflectors. A soft towel moistened with water will take the coating right off. It's not what the towel is wetted with it's the towel, rag, klenex, whatever. It's a vapor deposit (like soot on a hurricane lamp). If you touch it, it will come off.

Best advice... if you get a hole or break in your lens, replace it as quick as possible. Put some clear box sealing tape over the hole to keep the water and dirt out and you won't need to clean the reflector when you change the lens, But whatever you do, resist any urge to clean the reflector with anything.

res