Good question. I used to use overlapping strips of gorilla tape. It helped, but they'd wear off and you'd have to keep replacing them. I kind of gave up and just replace my paddle when the blades get too small. I'm not convinced it really made any performance difference but some people trip out about it. The only thing I noticed is that when you hit a rock there was less reverb.
Hojo was experimenting with some kevlar strips that I guess they use for hockey. Seemed like a cool idea. His first attempt failed to last, but he thinks with some more resin he may get better results.
Also I tried the carbon blade instead of the fiberglass blade in hopes it would wear slower, but they both seem to wear pretty fast. I don't think it's worth the extra money & weight savings (at least for a bent shaft) is miniscule.