Thanks Ghost, the cows fit pretty well in the typical old galvanized wash tub. I bent the sides so it looks more like a three pointed star. You can imagine, one point for the nose, and two for the horns. You aren't supposed to use fire on these tubs because of the toxic fumes, but mine is old has been used for cooking stuff for a long time, and I use it away from the house.
For the big skulls, I bought a 55 gal steel drum and found a guy that offered his plasma cutter and he cut the top off and cut two notches (not to be confused with Naches) in the sides so the heads fit down in the tub and the horns/antlers cradle in the notches.
The skulls fit better once the horn caps come off. For that, I just slow cook till they pop off with a little elbow grease. I live smack in Bellevue, so masceration (where the flesh rots in warm water) isn't an option for me on these big skulls. If you're careful, the fine turbinate bones in the nose all stay in tact.