Air compressor - you start the grip on the bar or throttle tube, then blow in by the flange to balloon the grip out and push it on. I just did two sets today, one on the street tracker and another set on my KLX650. Quick and easy.
Depends on the grips. The Malcom Smith Racing grips I got for the KLX say not to do any stuff on them.
I have glued them and still use the same technique. It just works. We used to blow Grab On grips (foam type) on bikes in abotu 5 minutes when I worked selling bikes at a shop. It took longer to get the stuff ready to do the grips than to put them on.