What is an [https://www.island-trade.com/iGlaco-Oleophobic-Coating-Kit-p159955720|oleophobic coating kit]?
Modern smartphones feature an oleophobic (oil-repellent) coating that protects the screen, improves smoothness, and reduces fingerprints.
However, oleophobic coatings can degrade or wear off quickly, and you will notice a patch of the screen tends to get greasy or dirty with fingerprints more easily. Also, many screen protectors do not feature an oleophobic coating, making them get grubby with fingerprints and grease.
There is a simple solution to restore your oleophobic coating, or to add an oleophobic coating (e.g. [https://www.island-trade.com/iGlaco-Oleophobic-Coating-Kit-p159955720|iGlaco]) to your screen or screen protector, to prevent fingerprints on your touchscreen. You can use an oleophobic coating kit.