Looking to darken the x-metal pieces on an XX TiO2 just a hair. Tried some of my gun oils and olive oil, no luck. I found a thread where someone put titanium penny's in oxi clean, but I don't want to dip my entire frame. I just got them back from a tune up refinish, so I don't want to send them back out, was hoping there was something I could wipe on and off. If not no worries. Thanks!