Back in the dawn of time... the 1980s B.C. - before computers, I bloody SWORE by by Stadler-Mars Rapidograhs. Speedball extra black, and pained in solids with Higgins Super Black. And I also was a "line builder" for variable lines. I never really got the hang of variable brush lines. But I also used the heavier lines for cut-lines.
Thank you for sharing, I am fascinated by fellow artist's process.