I built a walnut shelf and finished it with 100%, grade A, straight from the nut, tung oil. I used just a single coat and was happy with the way it finished so ended things there.
That being said, I continued to take a clean rag to the shelf to wipe down the shelf and continued to be able to get a little oil on the rag up to ~4 or 5 days after oiling the board.
For a next project, I'm going to use the last bit of scrap walnut to make coasters.
Because of the expected abuse they'll take being coasters, I'm thinking it would be a good idea to apply multiple coats of tung oil.
The question is, when to apply subsequent coats? Am I right in assuming I should continue to wipe down the wood and then apply a subsequent coat only after the previous no longer leaves the rag brown?