The issues you are experiencing with the paint running down the wall and not sticking to the drywall are likely caused by poor surface preparation. To prevent this from happening again, you should thoroughly clean the walls to remove any dirt, grease, or old paint residue. After cleaning, you may need to sand the walls lightly to create a smooth surface for better paint adhesion. Additionally, applying a primer specifically designed for slick surfaces or using a high-quality bonding primer can improve paint adhesion.

If you are dealing with particularly smooth walls that are prone to paint running, you can consider using a textured primer to provide a rougher surface for the paint to grip onto. This can help prevent the paint from dripping off the walls and ensure a more even application.

In summary, to address the issues you’ve faced with paint running down the walls and not sticking, focus on proper surface preparation including cleaning, sanding, and using appropriate primers designed to enhance paint adhesion on smooth surfaces. By taking these steps, you can significantly improve the paint application process and achieve a more durable and professional-looking finish in your bathroom.