Another option for you is to wax your gun. Lots of collectors do this. A popular choice is Renaissance Wax. It is available at woodworking stores, etc. Just like a car wax, it will put a barrier between your gun and the air. Very hard when it dries, and looks great.
Besides getting a pocket holster to keep the wax or oil from getting rubbed off, Don't forget the bore and internals. Run a jag with an oil patch down the barrel frequently or you'll get rust there, too. Whatever rust is on the gun, get it off. Inside the crane/yoke, DO NOT use sandpaperor anything - the fit of those pieces is critical. Use some Mother's polish or similar and it will come off with some hand rubbing. Be careful with the alloy finish as that is easy to scratch with any polishes or abrasives.
I have seen SS S&Ws from "marine" environments witha ligth coat of rust inside the yoke/crane. Let me tell you where else it is forming - inside your lockworks. I'd also periodically remove the side plate and polish/lubricate in there. Take the grips off to and clean/lubricate under there.
The rust is forming where the salt environment penetrates, then is trapped after your gun get's out of that environement (you go home) and dries. The areas with poor circulation "trap" the moist salt and keep it from drying quickly. This will also happen under the grips and inside the side plate. It is also very important to take your gun out of the holster when you leave work - just as the metal-on-metal helps trap the moist salt, so will the leather. It needs to air out and dry. If you leave the gun in the holster, you'll have MORE problems, not less. This si the reason you don't leave guns holstered in the safe for years on end. I have seen collectors grade "presentation" guns stored away for years untouched come out pitted because there was a speck of oil or a finger print on them before they were stored, with the lining to sit there and keep air from circulating and drying it.
Before removing your side plate the first time, learn how to do it properly, it's harder than just taking off the screws and prying it off. That will likely mar the top of the sideplate as well as help you loose your hammer safety. There area good "FAQs" that cover this step at the smith-wessonforum.com - very helpful bunch of people, also.
You're environment is very, very harsh, clearly, and you need to take some exceptional maintenance steps.
Hope this helps.
