What he said. If you buy a hank, getting them untangled and on the tube is no fun. When stuffing, you have to be careful not to over-fill them. If they are stuffed loosely, you can tighten it up as you twist your links. You'll have to remove some air pockets too, but that's no big deal. As you stuff (hopefully you have a dedicated stuffer, I can't imagine doing sheep casings with a grinder), the casing should be flying off the tube pretty quickly. Also, keep sliding the casings that are still on the tube out toward the end of the tube. If the casing is coming off the tube from the back, it causes too much friction, stretches the casing and they will burst. You should do this on all casings, but it is especially important on more delicate ones like sheep casings.