How to Make Acrylic Paint Glossy
Pour a small amount of varnish onto the paper plate. Dip a clean, dry brush into the varnish.
Apply smooth, even brushstrokes to the surface of the acrylic painting, all in the same direction. Do not overlap brushstrokes.
Wait for varnish to dry completely. If you want to add a second coat, make your brushstrokes smooth and perpendicular to the first set of strokes.