Depends very much on what the current finish is. For most, a good rub down with sandpaper (or similar) to provide a good key for the white undercoat (ideally 2 coats to ensure total coverage, more if required) followed by a coat or 2 of whichever topcoat finish is required.
If the final coat is to be a water based one (harder to clean and not as dirt resistant as oil based finishes), allow plenty of time (a few days) for the undercoats to dry and cure completely before applying the final coat. Personally, if I wanted a matt finish, I would apply an extra coat of undercoat after a gentle tickle with sandpaper and a wipe with a white spirit dampened cloth. Use top quality paints - you might save a $ or 2 in materials by using cheap stuff but once you add the time it takes to apply extra coats, any saving is wiped out!
If the brown colour "burns" through the undercoat, you'll need to either strip the item back to bare wood or give it a coat of stain stopper (a good hardware store should be able to advise which is best).