Dr. Bob Brier actually performed a mummification procedure in in 1994, and this was one of the questions that he sought to answer. After a lot of experimentation, he found that the crook that it has always been suggested was used to pull the brain out was actually used as more of a whisk, liquefying the organ before turning the body over and allowing it to drain through the nasal socket.

You can learn more about the whole mummification process in either his book, Egyptian Mummies: Unraveling the Secrets of an Ancient Art or through his lectures on the History of Ancient Egypt from The Great Courses. The lectures on mummification begin at 26, while lecture 28 describes how he engaged in mummification himself and what he learned from it.