If the damage to the polycoat isn't down to the metal, cold blue won't do anything -- as the various cold blues cause a form of rust to form (which is what "bluing" is all about.
The black from Birchwood Casey won't work well with the CZ, either, but it's closer to a paint the something that causes rust. That stuff IS us great for touching up black (anodized) aluminum frames that don't have polycoat. Cold Blue doesn't work in that situation, either.
I'm a long-time CZ owner and have tried just about everything over the years. Matte black auto body (or model) touch-up paint, thinned a bit, is the best solution for polycoat. Dupli-Color is an almost perfect match. (It also matches the black used on the Sphinx pistols...)
TunnelRat -- I modified my response above WHILE your were answering... The auto paint holds up better.
Last edited by Walt Sherrill; November 14, 2012 at 03:39 PM.