This is a great sample of how the animators and assistants at Disney worked in the past. Here you have a Milt's ruff of the Sheriff from Robin Hood and the cleanup touch up of the same drawing.
I am glad that the ruff was copied before it was cleaned up, otherwise we would not have this to compare because it was done on the same drawing.
Note how much information was already there in Milt's ruff drawing and what the assistant did by just erasing and connecting some lines and keeping the volumes consistent.
At that time, each animator had their own team of assistants that did the rough inbetweens and cleanup and they would work together for years.