I asked Greenhorn about this a few years ago. He gave me a very good idea about how to do it.
Clean all the big stuff off.
Simmer for awhile.
Clean more crap off.
Repeat simmering/cleaning(beer drinking) until it meets your standards. It will take a long time but it will be worth it.
Simmering...
Bob checking progress.
Once you get it cleaned up(and becareful around the fragile nose bones/sinus area) you will need to soak it in some of the crap women use to lighten up their hair color. I think a guy wants to use 40% hydrogen peroxide? Correct me if I'm wrong here.
Regardless it works great if you wrap paper towels around the base of the antlers so that the liquid gets up there but not actually on the antler itself.
It will take a day or two for the skull to whiten up and should look fairly natural when it's done. I'm not into the super white fake looking, glazy skulls and using the stuff Greenhorn recommended this won't be a problem.
Long story short it takes alot of work to get the skull looking good. I would only do it on a nice critter(or kid's first deer etc..), which reminds me, my little 4x4 from last Fall is still sitting in the garage with the hide on!