Tung Oil and BLO work by slowly building up and filling the pores of the wood grain. If you have ever spit shined a pair of boots you have the same situation. As the pores get filled up you can get a shine on it. Personally I just use the Tung Oil to do a couple of things for me. One - Seal the wood so that the real finish does not soak into it as much. Two Tung Oil darkens and brings out the grain pattern a bit. By sealing the wood you can top coat it with shellac or lacquer or Poly with little difficulty. The problem with either Tung or BLO is that it can take a long time to finish getting hard, sometimes years that is why I use it to seal and then top coat.
DW