While it might seem like daunting task, painting metal surfaces such as bulkheads, is not all that dissimilar from painting any other surface. If you know how to paint any other surface, then you will be able to pick up painting metal surfaces very quickly.
Strip the metal bulkhead of any previous paint that remains on it, if any. Do this by applying a layer of paint thinner to the painted areas and allowing it to soak for one minute before scrubbing the paint with a wire brush. Be sure to check around any bolts or rivets for small chips of paint around the edges.
Scrub the metal bulkhead with a metal brush or Brillo pad. This roughens the surface of the metal and helps with the primer application.
Prime your surface with two layers of primer. Allow the first layer of primer to dry before applying the second. This is to protect the metal surface from possible corrosion from the paint.
Paint the first coat of specially formulated metal paint to the metal bulkhead. Be wary of painting over bolts, nuts or screws. Painting over any rivets is OK. Wear a surgical mask and eye protection to protect you from paint fumes and potential blowback while painting.
Allow the first coat of paint to dry before applying the second coat. This layer is used to balance out the colors and cover up any bare spots on the bulkhead. Again, wear a protective mask and eye protection when painting.
Give the paint a couple of hours to dry. If necessary, apply a third coat.