We're only a bit into the 21st century, so I still draw schematics on D-size vellum, but I'm finally giving up on the old diazo/ammonia blueline machine to make copies for other people.
These drawings photograph poorly, but I've found a way that works pretty well: tape them to a window backwards, so they photograph by transmission rather than by reflection. Transmission is the way that the blueline machine worked. Low room light helps.
Irfanview can flip and tweak the image and make a pretty good pic.
I'm not sure why backwards helps, but it seems to.