I steel wooled my tunnel on my pro-x and polished it. The person that had it before me must have tryed to use some sort of acid cleaner to clean it up before and it looked like they had left it on there for quite some time.... either way it ended up etched. Apart from the steel wool, I used not even a quarter can of Never Dull on it and it looks incredible as compared to what it did. Its not even half of what any of the tunnels on here look like, but if you are lookin to spend a few hours on a tunnel just to better it a little bit, some fine steel wool and never dull will do the trick, just don't expect a professional look from it. Ill get some pictures and throw them on here. i think it took me like 3 hours of total work to do it... spent 3 days on it but it was mostly spent looking at the little bits i did to start off with, i was in awe to say the least lol