You need to finish the finish -- you need to fill the surface and make as smooth a possible before paint is applied. Think of the surface on a sheet of MDF and one notch better. The grain of the wood is showing through.
I often use Bondo as a filler sealer that will sand to a smooth clean surface - and if you are using an open grained wood, doing that before the final shear scrape or skew cuts helps get a perfect surface needed for a quality paint surface.
That should cleanup well and then think about how an airbrush might be used to highlight the shape.