When paint turns hard, it is usually because the paint has dried out. There are a few things you can do to try to soften the paint:

1. Add water to the paint. This will help to thin the paint and make it easier to spread. Be sure to add water slowly and stir the paint thoroughly to avoid lumps.

2. Use a paint thinner. A paint thinner is a chemical that can help to break down the paint and make it easier to spread. Paint thinners can be purchased at hardware stores.

3. Heat the paint. Heating the paint can help to soften it and make it easier to spread. You can heat the paint in a microwave or on the stovetop. Be sure to heat the paint slowly and stir it constantly to avoid scorching.

4. Sand the paint. If the paint is very hard, you may need to sand it down to make it smooth. Be sure to wear a dust mask when sanding paint.

Once you have softened the paint, you can spread it with a paintbrush or roller. Be sure to paint in a well-ventilated area and follow the manufacturer's instructions for painting.