I’ve noticed some artists working directly in sketchbooks, and I’ve also asked around about using gesso board. Recently, I came across canvas paper that can also be used in sketchbooks. Using canvas might be something I’ll try once I get more comfortable. From what I’ve learned, water-mixable oils tend to absorb and dry much faster on surfaces that aren’t properly prepared, which makes them harder to work with and can take away from the benefits of using oils in the first place.