Qualities of plywood vary greatly. If applying water media on thin plywood. Cradling or bracing is recommended to avoid warping.
Although you can draw or paint directly on the plywood panel with oils, watercolors, or dry drawing media, we recommend a barrier for most applications.
When painting with any acrylic paint, medium, gesso, or ground, we recommend applying 2 or more coats of Gloss Medium first to reduce support induced discoloration.
For oils, apply 3 or more coats of Acrylic Gesso or Fluid Matte Medium to reduce oil absorption.
Grounds (including those for drawing media and watercolors), gels, and pastes can be applied to alter the surface’s absorbency, durability, or texture.
Article: Plywood as a Substrate for Painting