I have slick sheared all my cattle since I started showing five years ago. As far as lines go, there are two options. You can either go with the grain of the cow (you wont get as close or clean a cut) and brush the hair down and use a ton of show sheen and pink oil. OR When you're clipping against the grain overlap your cuts. So instead of starting anew clipper line after a stroke, split line you already made in half and go from there... It will take alot longer but it cuts down on those lines. Also if you'd like, clip the cow one day, come back the next day and wash and clip again. Im sure there are better ways but thats what has worked well for me.