You want to remove all large chunks of meat, then set your galvanized bucket to boil, when the water is boiling add about 5 ounces of soda ash and then place the head inside the already boiling water, remove after 15-20 minutes, then dump the water in through an old window screen to sift any small teeth that may fall out.

Take 8 ounces of clorox and add to 5 gallons of water submerge the head for an hour, if you still have oil and grease then you want to use a degreaser to remove it , also take a large flat screw driver and remove the brain through the spinal cord hole,
After you degrease it , then you take hydrogen peroxide at 40% you probably need 5 gallons of it to submerge the whole skull for several hours then rinse and hang in the sun to bleach.
Total cost of chemicals will be in the $50 range, check with a taxidermist in your area and see what the cost would be.