DIAGNOSIS You're right to be careful. The QN85C screen has a strong anti-glare coating that can be damaged by chemicals or abrasive pressure. Static makes it attract dust like crazy.
FIX The only tools you need are a clean, dry, ultra-soft microfiber cloth (like for glasses) and maybe distilled water. First, unplug the TV to reduce static. Gently wipe the screen in a single direction with light pressure to lift dust. For smudges, slightly dampen a second microfiber cloth with only distilled water—never spray directly on the screen. Wipe gently, then immediately dry-buff with the dry cloth.
IF THAT DIDN'T WORK For stubborn spots, don't press harder. Instead, breathe lightly on the spot to create a slight fog, then immediately wipe with the dry microfiber. The tiny bit of moisture is usually enough.
HEADS UP Never use window cleaner, alcohol, ammonia, or any all-purpose spray. They will permanently haze or strip the anti-reflective coating. Also, avoid those "cleaning kits" with liquids. If you've already used a chemical and see a cloudy residue, it's likely damaged and won't buff out—you'll have to live with it.