I have several old Griswold cast iron skillets and camp dutch ovens. They are very, very smooth and hold seasoning well. There is no reason that such a surface cannot be achieved in an evening or two by hand. Amateur astronomers used to grind their own mirrors by hand (some still do). Some of the most beautiful lacquered surfaces I have ever seen were done by hand before the invention of sandpaper or machine tools. Tedious, yes...difficult, no.