Do you know what wood the outer
surface is? Is it teak or mahogany or what?The real answer depends on what the existing condition of the finish is which you describe as being: "lost all if it's finish". If it is an old varnished surface then liberal sanding would be disired to get down to the wood, possibly leaving areas where the old varnish seems good, then many re-coats. If it is a polyeurathane or Cetol or other product then sand smooth, wipe down with acetone (same for varnish to by the way), and re-coat with same. Old varnish yellows, curls up and flakes off wood. Cetol can turn darker or a greenish tint in a salt water environment (I assume your boat is in salt water but it is not clear from your initial post what waters you are in). Teak likes teak oil. Mahogany may prefer other oils before wiping down and eventually varnishing. If it is interior woodwork you could consider Tung oil before varnish for a lasting furniture like finish. Follow up with Butchers wax and it will look like one million dollars.There are books on the subject you ask about as well.Good luck.CalebD