I don't know what Dunlop 65 actually is so I can comment other than to say that Tru-Oil is a gunstock finish. It is designed to protect against things like sweat, water, blood and oil. I can't see a furniture polish hurting it.

On all of my rifles that are finished with Tru-oil (or any other gunstock finish for that matter) at the end of the day I simply wipe it dry with a soft cloth, before oiling the metal bits. I have never had a gun oil or bore solvent harm the finish.

On a guitar? I'd just wipe it down to get the sweat and skin oil off. You could apply a polish/cleaner but I see no real point.