Being a trucker, I have many hours of free time to think about ideas and how to make them real. I jot down idea's as they come to me. I'll rough sketch the idea, then think more about it, maybe have to make some modifications to my plans as I think about problems I might encounter, then I go build it. I wouldn't have a clue how to cad something. I just know what something will look like by experience. Straight line segmenting is the easiest. When you want different effects, it gets a bit bizzarro..like a large circle is designed as an oval in a blank. I was just making some new skull's and it's funny to look at the skulls before they are turned, as they look almost like conehead skulls, but when they are spun they widen out to be close to round, but not too round, as a skull wouldn't be a perfect circle. If you make a million cubes, unless you pie them like Sensai's, then some cubes will be wider than others when turned. If you put a thin slice on an angle, it is straight on two sides and curved on two sides, so if you don't want the curve you have to segment something else in it's place. Alternating curves produce scallops. It goes on and on. Once you do the designs, you understand what they do so you can create new ones.