Touch up black coating?

[crabo]

I am thinking about milling a couple of new slots in my barrel to give me some better optic mounting options.  The gun is a S&W Performance Center 44.  It has a matte black coating.  Any idea on what to use to touch it up after the machining?

Thanks,

Craig

[KN]

I use a liquid touch up bluing, (don't remember which one) for holes or crowns and such. Looks pretty good.   KN