In those days, I used to pencil pages in the finished size and then blow them up on a photocopier. I then inked on single-ply Strathmore on a homemade light box my Dad made for me. (Long lost in the fog of many moves.)
I didn't start inking on double-ply board until about halfway through the run of TOTB.
Because I was always laboring for myself, I never had to work according to any industry standard rules or regulations. To the best of my recollection, I've never pencilled a page directly onto the paper and then inked over my pencil lines.
Sometimes I still come across pages that were discarded for some reason and the photocopy is still taped to the back of the board.
I still have two store-bought light boxes and I rarely have any reason whatsoever to use either!