I need new grips and of thinking of getting some lock-ons. I used to ride dirtbikes and never had any problem of slipage b/c I cleaned the bars really well w/ rubbing alcohol before I put them on. Ive heard of ppl using grip glue and wire ties.
+1 for hairspray. Although I am not sure how long it takes to dry. Since it is kind of sealed off by the grip itself, it might actually take the grip a day or two to completely dry. I used it myself and it sticks very well.