[EricH]

I once did 2 or 3 sketches inside an hour, by hand (pencil, paper, ruler). I was able to turn 2D sketches into 3D interior/exterior view just by changing the line. 2 years later, one of the sketches is still floating around the team I did it for. Still no CAD for that one, that I know about...

Until CAD software can take a pen/pencil drawing and turn it into a 3D model instantly, both are very good topics to know.

Now, if I had to do those sketches using a T-square and other drafting tools, it would take considerably longer. It's also harder to modify them well.

CAD's strength is that you can change anything you need to and see how the parts fit together. Freehand sketches are fast, but usually not to scale. Drafting is to scale, but not fast.

These days, I'd start with perspective and freehand, then move to drafting or CAD.