As dabac said, remove clean with alcohol, reinstall with air or use alcohol as a lube.
I remove and replace lots of grips, and use air 95% of the time. When I don't use air it's usually because the grips are trash and are being cut off(the quickest way to get them off).
If you never want to remove them, or struggle mightily to do so, and have a mess to clean when they are off use hair spray.
I have a buddy that is a professional bike mechanic, he uses WD-40 to put grips on, he swears by it.