I remember the days BC, (before computer) when the salesman would come in with specs wanting to see color and an artist would sit down with pencil and color pencils and do a layout, then the salesman would drive back over to the customer who would change a color, calling for another hand drawn layout, another trip across town etc. We've come a long way!
I would do a pencil drawing on vellum, stick it in the metal tube with blue print paper, with the ammonia at the bottom, take the blue print and using Design Spectracolor pencils, color it in. You could get some great blends with those pencils. For Archtitectural finish drawings such as the poster did, I would to watercolors or gouache.Sounds like a strange way to make layouts.... even back then.
The standard was to sell the B&W design/layout/logo first. Then we would take the black & white, make a slick and put tissue paper over it and do partial coloring. Sometimes one layout/design would have 20 or more tissues layers.
As for darkening the room, in my first shop, we had no windows. It was a huge four bay garage, so making it dark was natural. Our second shop, we installed awnings on the inside of all the windows and would draw them closed when needed..... or waited til nightfall.
Me too. Did you have an electro-pounce? Zzzzzzzzt! No fun getting up early to use the projector because we couldn't make the room dark enough during the day. lol. I miss my quills and my airbrushes and the wonderful smell of One Shot!