The kit is in the white, so I'll probably rust blue the steel or brown it.I have heard of people using that to remove the original bluing,and then using cold blue to apply a splotchy new finish. But that is not how a blued gun ages. The original blue remains until it is worn away, which is the finish I try to replicate a new part I might add to an old gun. Use fine abrasive paper and a buffing wheel with fine compound on the blued areas. Just removing the original finish from a gun is not "aging" or "antiquing" it. In the real word, the high areas get worn away quickly, but the recesses might still contain some nearly perfect original finish.
Another common mistake is to have perfect wood and screw heads. In real life the wood will get beaten up, so take that newly finished grip and sand off finish in the high areas, and thin the finish in other areas. Deliberately mutilate the screw heads. When you are done with that, place your revolver on a concrete surface. Take your rustiest, nastiest log chain and hit it a few times with varying force. Roll the gun onto the other side and repeat the process.
Cold blue will put an artificial, but quick, patina on brass. Use steel wool on the high areas to expose bare brass.
Now your gun should look more like a well-used antique.