One shop I worked in used Meguiars Mirror Glaze #9 Swirl Remover to remove scratches and gunge from the surface of instruments and make them shiny and new looking. CAREFULLY USED, it brings out the shine in matte lacquer finishes. My new Larrivee has a matte finish on it (really hate it) but is coming up shiny on the neck where I play it, so I'll probably buff up the whole guitar to get the nice gloss on it that will also bring out the wood grain nicely. It's up to you. If you want to polish your guitar, there are guitar polishes on the market that work just fine. They are, after all, formulated to be used on lacquer finishes. There's nothing wrong with a protective coat on the instrument, especially if you have very acidic sweat. Also, just because the guitar says Martin on the headstock doesn't mean you have to put it in a shrine. It's just a guitar. Play it. Enjoy it. If you like shiny, then make it shiny. If you want to invest money in something, try soybean futures. Investing in guitar futures is evil.