I used hair spray with good results. As for the yellowing.....I've no luck getting them white but the yellow colour goes great with the gold trim on the bike :-)
Ian
p.s. when I was young and stupid (having just acquired my Goootsie) I thought that the original grips on it were cheap aftermarket ones. I cut the throttle grip off. AHHHHHHH!!! All was not lost though. I used some contact cement and glued the grip back together and it has held well for over three years now :-)