Whether to brush or roll stain on wood depends on the project and your preference. Brushing is ideal for smaller, intricate areas and offers more control over the application, ensuring thorough coverage and penetration into the wood's grain. 

Conversely, rolling is efficient for more extensive, flat surfaces and can save time. However, it is not always the best fit for textured or uneven wood. Some projects may benefit from combining both methods, using a brush for detail work and a roller for broader areas. Ultimately, the choice between brushing and rolling depends on the specific requirements of your staining project.

Pressure-treated wood lasts at least 10 years, but with the right care and treatment, it can last as long as 40 years. Painting the boards is one way to increase the lifespan of pressure-treated wood. The layer of paint provides extra protection for the wood against the exterior elements and insects.

For the longest-lasting exterior paint, consider acrylic or enamel (oil-based) paints. Acrylic paints, including acrylic latex and acrylic enamel, are known for withstanding harsh weather and sun exposure. Enamel-based paints are also one of the most durable options available. While latex paint is common, it typically has a shorter lifespan than acrylic or oil-based options. The paint's finish also affects its durability; a higher gloss finish is generally more durable. For resistance to moisture and cracking, matte and satin finishes can be effective, while a high-gloss acrylic or oil-based paint offers a combination of maximum longevity and durability.

Whether you can paint over your existing paint depends on what’s on there. Most of the time, you’ll want to sand down or scrape off the paint that’s currently coating your surface. Epoxy paint, for example, won’t let new paint stick to the surface. Latex paint is more forgiving and will accept a new coat, but a primer is recommended if you’re switching colors.