If you haven't installed a thousand pairs of scooter grips yet, don't worry...you will.
Grips are usually one of the last things added to a scooter during a built and since they are a relatively minor part, it's really frustrating to scooter kids when they have to wait for grips to dry. Traditional methods for installing grips involve using some kind of relatively quick drying lubricant to allow the grips to slip on to the bars. I have typically used a light mixture of dish washing soap and water, mostly water, to install grips. Windex can also work and I've heard of people using spray paint as well because it dries sticky and acts like glue to a certain extent. I would personally avoid spray paint because of the PAINT aspect of it, which can ruin the finish on your bars and over-spray on to anything around you. It's messy and unnecessarily mars your parts.