I cook them too but it better to simmer than get it to a hard boil.
1.It is always best to skin the head and manually remove as much meat as possible.
2.It helps a ton if you then let the skull spoil for a few days to a week.Don't let it dry out as this increases cooking time.Either wrap it in plastic,shrink wrap or put it in a bucket of water.
3.Put it in to simmer,with a hanful or two of baking soda and check it at least every hour and pick off anything you can.After some time and all tissues are getting loose,a garden hose can be used to flush out the brains.You can flush out the nasal cavity but keep the water pressure real low so as not to damage the thin nasal bones.You can flush them from the rear,underneath and then from the front.Easy does it.
4.Continue this process untill you have everything off it.If the water gets real dirty,halfway through,change it for clean and more baking soda.A little dishwashing soda helps too.
5.If you have to stop before it is cleaned,don't let it dry out.Put it in a bucket of water where dogs can't get to it and resume when you can.
6.The more spoiled that meat is before you start,the faster it falls off.You don't want to start with large pieces of meat as the outer protects the underlyuing stuff and the baking soda water can't reach it.Take the time,beforehand, to trim off 90% of the meat.If your head is already dried out before you cook,put it in a bucket of water till it is rehydrated again.
7.After cleaning and letting it dry,you may see grease spots.Deer aren't bad for this but sometimes...The spots look like wet areas,when the skull is dry.Soaking in a strong water/Dawn detergent solution might work but degreasing can take a long time,weeks on a very greasy skull.I have had better luck with acetone but that can get expensive for just doing one skull.Deer may need no degreasing but yu can recognise it if you need to.
8.You may need to bleach after getting to this point.I use a strong paste bleach from beauty suppliers or taxidermy suppliers but some use hydrogen peroxide from the drug store and submerge for a period of time.
9.After they get to this stage,I seal them with Future floor finish.Future is a clear,non yellowing,water based finish and dries to a satin or semi gloss,depending on one or more coats.You can also seal with watered down Elmer's glue.You can spray them with clear spray but make sure it is a non-yellowing spray like acrylic.Polyurethanes are and will yellow.
10.It is important to get them CLEAN,if you intend to have them in your house.A skull with bits of meat will inevitably attract dermestids and or clothing moths that,after cleaning your skull,will migrate to your mounts and wool clothes.Take a little time and like any job,lay the foundation right and you will have a professional quality outcome.