I have had success with gluing but still treat it as a temporary fix. If the slippage isn't total, that is it slips at medium to high revs, glueing might work. Dig out a channel of the rubber compound and fill with glue. I used Araldite but I can't suggest it's the best for the job because there must be some flexing going on between the shaft/rubber/prop. Anyway it worked until I bought a new one some weeks later so I keep the old one as a spare.