Yes, you can paint a picture on Masonite.
Masonite is a type of engineered wood composite made from wood fibers, typically formed into a dense sheet using heat and pressure. It has a smooth, hard surface and is often used as a building material or as a substrate for painting and other artistic applications.
First, remove any dirt or debris from the Masonite. Then you can paint on Masonite if you apply three or four coats of gesso first. If the surface of the Masonite is smooth, then use light sandpaper to rough up the surface before applying the gesso. This will allow the gesso to adhere better to the board. If you are intending to produce a super-smooth surface to paint on, then apply each gesso layer thinly with a soft brush. Wait for the gesso to dry completely before painting. Be aware that if you apply the gesso thickly, the ridges of the gesso will appear in your painting if you apply thin layers of oil paint over it. This appearance is neither correct nor incorrect; it’s just an effect the painter needs to be aware of.
Apply each layer of gesso at different angles. This will result in a smoother gesso surface: