Yes the 60 day "dry out" period applies to skulls for B&C as well as antlers.
FYI, here is a link to the bear score sheet on B&C websites;
http://www.boone-crockett.org/bgRecords/bc_scoring_bear.asp?area=bgRecords&type=Bear
Just like any B&C scored animal it must be scored by an official B&C measurer, photo/forms, fees, etcmust accompany the official score card upon submitting your trophy to B&C. A list of requirements,scorer's,etc can be found on the B&C website.