DIAGNOSIS Smearing happens when you're using a dry cloth on oily fingerprints or when the cloth itself has picked up dust and oils. The ProArt has a standard anti-glare matte coating that you don't want to damage.
FIX Here's the shop-approved method. 1) Unplug the monitor and let it cool. 2) Use a dry, clean, new microfiber cloth (like for glasses or camera lenses) to gently wipe off any loose dust. 3) For smudges, dampen a second clean microfiber cloth with distilled water only. Wring it out so it's barely damp, not wet. 4) Wipe the screen gently in a circular motion. 5) Immediately use the dry side of your first cloth to buff the area dry before the water evaporates and leaves spots.
IF THAT DIDN'T WORK For stubborn spots, you can use a 50/50 mix of distilled white vinegar and distilled water. The mild acidity can cut through oils. Apply the same way: a barely-damp cloth, followed immediately by a dry buff. Never spray liquid directly onto the screen.
HEADS UP Never use window cleaners, alcohol, ammonia, or abrasive cloths (paper towels, old t-shirts). These will permanently damage the anti-glare coating, leaving shiny patches or haze. The goal is to use the least aggressive cleaner that gets the job done.