wet the inside of the grip with tap water and slide em on.
They'll firm up within several hours once the water is gone. To remove them later pry the grip/bar joint open a little and drip some water in. Work the grip about and the water in an off they slide.
+1 for Hairspray.
I haven't done it for ages, and for getting them off you I think you can put the tube from the RP7 in the nozzle to get right underneath the end. They are slippy for a minute or two so you can adjust them, and then they fix firm.