I have just done some of the woodwork in my 86 Sovereign
, and I used my favorite varnish mix - 50% Watco Natural Danish Oil, and 50% Varthane Gloss polyurethane (although any good varnish will do).
You will want your wood as clean as possible first. If it truly is just an oil finish you can wipe it down with turpentine. Apply the varnish mix with a cloth, keeping the excess wiped off as you go. Allow to dry throughly, apply at least one additional coat, sanding first with 400 or 600 wet or dry paper. Rub down the final coat with a cloth a minute or so after applying the final coat. Dust is not much of a problem, as it will just rub out.
This gives a finish that is not as "dull" looking as a straight oil finish, can be wiped down with any usual cleaner, and scratches can be touched up anytime by just wiping on some more, and looks very professional. The polyurethane will give the wood protection from water (although it will NOT be waterPROOF). For more shine, use a higher percentage of polyurethane to the oil. For less, use more oil.
Open all the windows and vents
I have only been using this varnish for about 15 years, so cannot personally vouch for its longevity, but as far as I can tell it should last roughly forever.