For the outside, I'd use Flitz polish. Its only slightly abrasive, and uses chemicals to clean the nickel finish. (CZ recommended it for its nickel-plated weapons, which is how I started using it.)
Many of the newer nickel-plated guns don't have a copper undercoat and ammonia is not a concern for those plated weapons.. But it can be a problem for older guns.
There's also a small device that you can get from Brownells that looks like a wire mesh that you can put on a cleaning rod to pull/push out lead.
There are also chemically treated cloths that are great for cleaning off the front of the cylinder and can also be put on a jag to clean the barrel. (Cut off small patches, and seal the remainder up in a plastic bag to keep them chemically moist and active.)