Some have used a heated pressure washer to blast the worst off, but I'd rather take my time by hand--or at least soften the meat up with a boil beforehand. 8 hours seems awfully long...You can cut off a lot of stuff before starting the boil, including sawing off the lower jaw and opening the base of the brain cavity more. You can add some borax to the water. Aside from being persistent, you could always try maceration or dermestid beetles. Not faster, just--perhaps--easier. A 3% peroxide soak will lend bleaching effect but will also do wonders in loosening up any leftover pieces on the skull.