Well, I've used hair spray all along as well, but, after giving it some thought and after trading a few emails with Rich (MOB) I think he is right and keep in mind I live in the PNW and ride year round, rain or shine, as well as a KLR and YZ450F. If rain gets inside the grip area the hair spray will turn to snot, something I dont need happening right in the middle of a rough stretch. Give it a try, spray some HS, let it dry, then get it wet. Might as well be vasoline. I aint waiting on it happening to me, no more hair spray on my grips.
YMMV and all that yada.