+1 on Fingers, Pulp and Noz
Ballistol, bore butter, etc are crucial items to everyday shooting. It is the residue that starts the corrosion process, if you use bore butter over the loads, or a lube pill, etc, then that residue will already be mixed with a compound that will inhibit its action on the metal.
Add to that a liberal spray down with Ballistol after your shoot and you shouldnt have to worry.
Make sure that the Ballistol gets down between the frame and the hammer, into all cylinders, down the bore, etc etc, anywhere that powder gets.
I recently came back to Black Powder after nearly 4 years. Occasionally I have been getting one out and putting a cylinder through, then Ballistol and back in the holster. The only 'rust' that i noticed was that the Ballistol oil had turned a dark 'rust' color.
This last weekend, I processed all the revolvers through warm water, full strip and clean, and bake. Checked them afterwards, there is a little frosting in the barrel, and some over the face of the cylinder. Thats nothing thats going to affect me.
I also believe that no matter how anal a person is with a BLACK POWDER firearm, you are going to get some rust at some time.