What are the best application techniques for achieving a smooth finish with wood stain oil?

The best application techniques for achieving a smooth finish with wood stain oil include using a clean brush or cloth to apply the stain in the direction of the wood grain, allowing each coat to dry completely before applying the next one, and sanding between coats to remove any imperfections. Additionally, wiping off any excess stain and using a topcoat or sealer can help enhance the smoothness of the finish.