Fans did a lot of the same things. I've been using a computer to draw schematics for no more than maybe ten years, but before that all of my drawings were by hand and using the drafting skills I learned in high school in the mid '70s.
I have to grant that, alright. The older drawings at Cygnus were done by hand. And I myself took a drafting course in high school in the seventies, and it influenced my own drawings of STAR TREK sets and props. But FJ was a full-blown professional and (swimming pool, bowling alley etc. aside...) it really showed in his drawing.