Below is an interesting page from The Art of Show Card Writing published back in 1919. “Showcards” were what they called temporary signs made from cardstock that were displayed in store front windows. (So it’s essentially a sign painting book.) It depicts an artist at work on a sign using and airbrush and a foot pump compressor. The text offers some technique advice that is still relevant today. (Well, minus the foot pump.) You can find the whole ebook version for free on Google Books.