The best method for painting a garage door depends on the door's design and the finish you want to achieve. For the most professional-looking finish, especially on doors with panels or intricate details, a paint sprayer is an excellent choice. It can easily get into hard-to-reach places and provide a smooth, even coat.
If you don't have a sprayer, or if your door is flat, a combination of a roller and a brush is the most effective approach. Use a roller for the large, flat sections to cover the area quickly and efficiently. For the best results, experts recommend a roller with a nap between ⅜ and ¾ inches thick; natural fibers can also help ensure an even coat.
A brush is essential for handling the finer details. Use it to paint grooves, angles, small panels, and the edges of the door where you need more control.
Regardless of the tools you use, it's a good idea to step back after the main application to review your work and use a detail brush to touch up any missed spots.