I found the best rubbers are SYR Soft. I've tried Unger, Pulex, and Ettore, I'd say ettore is the nicest, but is expensive and doesn't last very long. SYR is the perfect balance. Very sharp edge, and lasts long enough.
I buy them in bulk, they are individually wrapped in plastic, no talcum powder or any of that mess.
Cut them down with a very sharp scraper blade, using a straight down guillotine method. Works like a charm.