I would say he uses a hole saw on the rear of the skull where the spine enters the base of it.
It doesn't take long for brains to stink,but if it is cold,wait till you get home and do it. Are you going to skin the head out too?
Are you going on a guided hunt and how are you getting there? If it is guided ask them to help you or even do it for you?
Also,the best of luck to you on your hunt.