Yes , they can be seperated ... just use plenty fairy liquid to act as a lube (oooooh errrr
)
I have always cleaned my grips with swarfega and a tooth brush ..... come out great
Having said that , i have done a set of the Fuan's with white sleeves before and to get rid of that browning is tough , I never got shut of all that , it seems to have soaked into the rubber