If you keep building up coats of CWF-UV the final result will be disaster. Try a quick clean then another coat, if that what your customer really wants.
Tung oil is a natural oil found in tung nuts. There used to be many tung trees in Lousiana but were wiped out by a hurricane. All tung oil now comes from China and S. America. Oiticica oil from Brazil is also used on decks. It comes from the Rosewood tree.