How wide of a brush should I use?

The best answer is whatever you feel comfortable with. A bigger brush holds more paint and applies it more quickly, but it is also harder to control.

Are you using the right brush?

Check your state and local codes before starting any project. Follow all safety precautions. Information in this document has been furnished by the North American Retail Hardware Association (NRHA) and associated contributors. Every effort has been made to ensure accuracy and safety. Neither NRHA, any contributor nor the retailer can be held responsible for damages or injuries resulting from the use of the information in this document.