In an attempt to try to clarify the term DISGUISED GUN in the Republik of New York, here’s the exact definition of a DISGUISED GUN, as per the NYS Penal Law:
“Disguised gun” means any weapon or device capable of being concealed on the person from which a shot can be discharged through the energy of an explosive and is designed and intended to appear to be something other than a gun.
So refinishing a firearm, but not trying to make it look like a toy or some non-firearm item should be ok. I understand the intent here, don't want perps to make their pistols look like toys or something else so as to not attract attention until they use them in a crime.