Dust with air hoist first, and then gently wipe with lens paper, suede or lens pen (lens pen is better than lens paper and suede). Otherwise, the glasses cloth can make do, it must be light, and be careful not to print fingerprints. Direct rubbing without blowing will scratch the mirror surface, and it is more troublesome to make water marks when breathing. Try not to use detergent to avoid damaging the lens coating. Just wipe the handprint, and it will be clockwise from the inside out after all. It is best for a SLR to have a UV mirror and an ordinary DC. I suggest you don't remind me too much that many people are unhappy.