How can polyurethane be effectively applied over paint to enhance durability and protect the surface?

To effectively apply polyurethane over paint for enhanced durability and surface protection, follow these steps:

1. Ensure the painted surface is clean and dry.
2. Lightly sand the surface to create a rough texture for better adhesion.
3. Apply a thin coat of polyurethane using a brush or roller, following the paint's direction.
4. Allow the polyurethane to dry completely before applying additional coats.
5. Sand lightly between coats for a smooth finish.
6. Apply multiple thin coats for maximum durability and protection.
7. Allow the final coat to cure fully before using the surface.