Re: Matte finishes?
The bluing is not roughed up but rather the roughed up spot needs to be blued.
Bluing the metal is the step done right after finishing the metal to your desired level (matte, mirror, etc.). For instance if it has a matte finish and just needs touched up, you would just apply cold blue to the spot you want to blue. If the finish was somehow rubbed in a particular spot you would have try to spot sand the place to match the rest of the finish and then blue it. I wouldn't advise this as it would likely stand out like a sore thumb or at least no worse than if you just applied cold blue to the spot needing reblued.
Once blued, nothing is done to the gun other than cleaning, oiling, and reassembling.