Here's what I do- I place them in a trash can that has a couple of inches of water in it, then cover the top with a trash bag. During the hot summer months, I can usually pull the horns in a day or two. When it's cooler, it can take a week or two. When you pull the horns, twist and pull at the same time. Be sure to clean inside the horns, and use borax to bug-proof. Then, like already said, cut the cores down to about six inches, simmer the skull plate until clean, then bondo or expoxy the horns back in place.