One of the reason's I attended Carol Marine's workshop was to use oil paints and mediums for a few days and get a better 'feel' for them. We all know they dry slower than water-based acrylic; I have the smudged student work and colorful fingers as proof. Waiting at my gallery is an unopened box of alkyd paints. These dry faster (4 hours or so) and are oil based. I will report on those.
As oil is tempting me to its embrace, I think about all the half-squeezed (some neeeeearly solidified) tubes of acrylic in my studio. I now apply them to the larger, 100% rag mat board scraps. I mix some neutral mid-value grays (warm or cool) and rough brush them onto the board surface and let them dry. That surface takes more paint (oil or acrylic) and the rough texture grabs pencil or pastel marks. The ink bottle on the book is a value study in oil on one of these prepared boards. The striped
composition is another of those boards; I painted it as I cleaned my oil palette