Tung oil finish is actually a thinned wiping varnish, with god knows what added to it. I bet it's pretty runny? I would try mixing it with the varnish to thicken it a bit, since you're going for an oil finish effect anyway. Note: pure tung oil (or decent linseed oil* for that matter) isn't likely to be found in the local hardware store or big box emporium. It has to be ordered in from the outside world.
If the "feed and wax" has petroleum distillates in it I wouldn't use it. That kind of product is designed to separate housewives and cleaning ladies from their money. It gives a beautiful easily applied effect that is temporary at best, resulting in repeated applications to maintain the glow. That just means you're piling more and more petroleum based gunk onto the wood which breaks down the UV protective qualities of the finish and attacks the wood over time. Stay away from it if you can. Seek out a good paste wax. Johnson's is an old stand by and can often be found in grocery stores. Stuff like Butcher's, Trewax, Renaissance, etc. can be rounded up online- they're all good. Don't skimp on the wax phase of an oil finish project, for therein lies the only real moisture protection you're actually giving the wood.
*Boiled linseed oil you get off the shelf is the lowest grade oil from the linseed pressing/refining process, with metallic compounds added. Better to seek out artist's oil from an art supply store- it's pure. Then add a drop of Japan drier (from the same supplier) to speed its curing. Can be substituted for pure tung oil for the exact same effect/utility.
