I would take a wire brush with some Hoppe's and some elbow grease, it worked with my CZ-52.
The advantage of using boiling water in the cleaning process for corrosive ammo is that the water evaporates almost instantly. It also leaves the barrel scorthcing hot, which I believe helps with the chemical action of the Hoppes, or whatever other cleaner you use. With normal cleaning after the water, there will be no moisture in the bore; no water, no NEW rust.After the hot soapy water you need to use a water dispersing oil like WD-40. Then clean that out and put a protective oil in there to provide a barrier from the air.