Disassemble the frame, and clean it using basic household cleaning supplies, such as dish soap and a dry, clean cloth.
Remove large chunks of rust or paint with a wire brush. Sand your bed frame to remove any additional rust.
Apply a coat of primer with the paintbrush to the entire frame, and allow it to dry.
Clean your paintbrush.
Apply a coat of water-based paint -- muted palettes work best for a more authentic look -- to the entire frame, and allow it to dry. Depending on the color you choose, additional coats may be necessary. Allow each new coat to dry before applying the next.