John by far the best way to clean a skull is to do the following :-

Clean as much meat, muscle ect off the head.
Buff heads will usually pop the horns of with a little help from a rubber mallet especially in the tropics after a few days in the sun.
Oil horns with neatsfoot oil
Boil the head in a mixture of washimg soda and water.
Most of the debriss can be scraped off or washed off with a high pressure hose.

The main reason for using WASHING SODA is to stop oil or fat staining the bone...

This is by far the best method and many taxidermists in the US use this method on a variety of animals......