Hey, I've got a warmoth dinky-J that has a tung oil finish. I want to add a thin layer of wipe-on poly for a little more protection. The body needs to be cleaned up a little bit, but overall it's pretty good. Do I need to prep it at all-- aside from cleaning it-- before applying th e wipe-on poly? Can I just put it on over the tung oil? The tung oil is a very thin layer and pretty dried out. thanks!