15 yr old tung oil.#1-liquid sanding/deglosser, oil based primer, oil or latex paint topcoats or….?
Your question is not really clear! Please state exactly what it is that you want to paint over???
To paint over Tung oil you will need to clean the surface really good (soap and water- rinse well), (any sanding need to be done before the deglosser), wipe with a deglosser (Paso is best) and double prime with an oil base primer. The reason for 2 prime coats is that the first will dissolve a little Tung oil and the second will provide the perfect seal. After that you can paint with any good paint, oil or latex. I recommend oil based paint for furniture, for its hardness and better overall looks. Hope that helps.