Finally, sand again after the second coat has dried to get the aged look you desire. Finish up with a dark gel stain used as a glaze to add a dark layer.
Although milk paint adheres very well, water or other liquids will leave stains on the dried paint. So it’s a good idea to apply a clear finish over the paint, such as lacquer, polyurethane, or shellac.
While the process is pretty straightfoward, it requires a little practice to achieve the right look.