Maggie's Farm

The finish used needs to be appropriate to the thing to be finished. Tung oil, while appropriate to Danish Modern furniture or perhaps wainscoting or some sort of paneling , is useless for anything else.
For some of the items mentioned in the post and comments:
Piano--lacquer, preferably nitro-cellulose.
Gunstocks--Linseed oil or, oil varnish, good oil varnish can only be had from violin maker suppliers these days , or make it yourself.
Antique furniture, formal, pre 1830- down to Queen Ann, or in those styles- French Polish. ( or French Polish anything you would like very shiny)
Antique Furniture, informal- Shellac and wax.
Antique furniture, primitive--wax

The old rule for linseed oil on gun stocks is: 1 coat per hour for a day. one coat per day for a week, one coat a week for a month, one coat a month for a year.
This will produce a very high gloss, incredibly durable finish that looks like many coats of hand rubbed varnish but will stand up to weather and abrasion. Well worth the time invested.

The article on wax is excellent only I would recommend beeswax instead of the commercial products mentioned.Beeswax is inexpensive, easy to prepare, can be used as a finish, cleaner or polish, depending on the ratio of wax to solvent and produces a magnificent shine.