I also used Caran d’Ache Crayons on my work. They were a waxy crayon that went on very smoothly and opaquely if you wanted them to. You could blend them with your fingers and they would dry to the touch and not smear after they dried. The same company made an oil pastel, but it never seemed to really dry. I would use them quite a bit for background textures . One day I had finished a job, and it was leaning up against my flat files, ready for me to flap it and ship it that night.
My 5-year-old son poked his head in my door and laughed as he squirted me with his water pistol. I laughed too until I noticed that the overspray had hit the painting, and when I tried to dab it up, it only removed the colors where the water drops were. At first I was furious, and wondered why these things always seem to happen within hours of deadline? But as I dabbed at it, I realized that I could never really fix it. So instead, I splattered more water on it and dabbed off more color. It was a major improvement to the work, and I began to use it on many pieces from then on.
I just looked them up and they are still manufactured. Called Caran D’ache Neocolor II Artists’ Crayons, they are water soluble. Their strong pigmentation allows light colors to cover dark colors and vise-versa. They are soft enough to blend with your fingertip, yet much firmer than oil pastels. Yep, that’s the way I remember them!