Doing marker renderings for comprehensive ads and storyboards is very much like painting watercolors. If an artist is familiar with this medium, marker rendering can be a breeze, except for the brutal deadlines, of course. Often when I take a trip I paint watercolor sketches, below are some examples.
I traveled to Sudan in 1971 and this is a sketch that was done in Khartoum.
A watercolor sketch done in Cairo.
Another sketch painted in Cairo, a scene from the hotel window.
A sketch of my wife, Jeanne.
These paintings were reproduced in my book, Art & Illustration Techniques that was published by Watson Guptill in 1979. It's a book about commercial and fine art painting techniques and is still available on the internet and in used book stores.