If it's the LCD surface itself (matte finish plastic) you can just use 50/50 IPA and a soft cloth. It will strip any fingerprints or detailing overspray and clean it right up. You should need to clean this often. Other products will leave behind coatings, oils or "protectants" and interfere with the matte coating of the display. It will be more reflective and show an unevenness even more easily. I usually find it's easiest to strip it and leave it clean. I also find cleaners like Stoner's Invisible Glass work OK and leave nothing behind on LCDs.
If you have a glossy plastic top coating, just use glass cleaner or plastic polish, not a product meant for vinyl.