1. Burying - This one is pretty simple. Find an area in your yard where you don't mind digging a hole and bury the shells about 18" down. The reason for the depth is so animals will not find them and dig them up. Also you or your neighbors won't smell them. Let them remain buried until the insects, ants, larvae, worms and bacteria remove all the tissue and they will darn near polish the inside of the shell. But, this could take as long as a couple of months. The longer you leave the shell buried, the better the job our little friends will do.
2. Freezing - If burying does not work for you then this method well do the trick and is another pretty fast way to go. Place the shells in a water-tight bag then place the bag in a plastic bowl or container of some kind and cover the bag with water. Place it in the freezer and let it freeze solid. I would suggest at least twenty-four hours. I usually let mine stay for forty-eight. When you are ready to clean the shells, allow them to thaw to room temperature. After they are completely defrosted (Don't get in a hurry!) You should be able to grab hold of the critter and gently slid it right out of the shell. You will still have to do the Vinegar and water soak and the warm soapy water wash then fresh water rinse but you will have a nice clean shell.
3. Boiling- Take a pot of water large enough to hold the seashells you are cleaning. Fill it high enough so that there are at least two inches of water over the shells. Bring the water to a rolling boil and let it boil for a few minutes. The more and larger the shells, the longer you let it boil. A shell the size of the average fist should boil for about five minutes. Two that size maybe eight minutes. Judging when it is done comes with time and experience. Don't get carried away and figure I have ten shells so that must be an hour’s boiling time! It's not, maybe twenty or twenty-five minutes is the longest I have ever boiled a big batch of