Antlers are made of bone, just as the skull. If you can accept the slight buffering of your pH, they work well in a tank. If you found some shed antlers, all they need is a quick scrub to remove dirt. If you have an entire skull with antlers attached, you must ensure that all soft organic tissue is cleaned from every nook and cranny on the skull. This means not only the brain, but also all the tiny channels through the skull which house various nerves and other tissues.
You can do this by boiling, picking, scraping, boiling, picking, scraping, etc. A high pressure waterjet like a pressure washer will help, but will damage some delicate bones such as within the nasal cavity. The easiest but slowest way is just to immerse the skull in a pail of water and leave it in the sun for a few days or weeks. This pail will need to be as far away from your house as possible! The soft tissues will decay, soften and fall off, with some help from a hose. As unpleasant as it sounds...and is!...this is a very effective technique and is used by many taxidermists, who refer to it as "maceration".
Once it's just clean bone, you can lightly simmer it for an hour or so in water with some dish soap added. This removes the odour and a lot of the grease that might be soaked into the bone. Let it dry in the sun, and you should be done.
If this is a fresh skull, there's a lot of smelly junk that needs to come off. If it's been in the fields for a couple years or so, it's probably 90% cured and very little effort will be required to make it safe.
