if you keep ya gun well oiled and maintained then rust should never be a problem, i would suggest sending it to Arson's cleaning service, he cleaned mine so good that when I got it back it didnt have any fingerprints and he scrubbed it so hard the serial number came off , great job.
soak the gun in a big bucket of Ammonia, and add equal parts of bleach, watch it carefully for about 20-25 minutes and then remove