I did something similar for a while with a drafting setup. One thing I liked about it was the utility in simple visualization techniques like drawing quickly in

I did something similar for a while with a drafting setup. One thing I liked about it was the utility in simple visualization techniques like drawing quickly in perspective or in various media. After doing that for a while, I found Inkscape and Free mind/Freeplane to be pretty reasonable alternatives that are still digital. Even in plain text mode I learned later that there are some practices that also help the big picture emerge faster, so the spacial effects aren't as necessary in many cases. Still, it's fun sometimes to get out the supplies and work in that way...