I did a skull mount for the first time last year. There are a lot of different ways to do it. This is how I did it.
First, I skinned the skull and removed as much meat as I could including the eyes and brain. Then I simmered it for several hours, removing it and scraping meat away every hour or so. Next, I removed it and took needle nose pliers and pulled out anything that wasn't bone. There is a lot of junk in the nasal passages. I then soaked it over night in hot water with dawn soap. The next day, I did some final scraping and gunk removal. Finally, I soaked it over night in a heavy duty peroxide solution. Do not get peroxide on the antlers, it will bleach them. I took some peroxide and mixed with baby powder to make a gelly that I brushed all around the bases and any part of the skull that wasn't submersed. This was the end result.