Try LPS-2 for short term. Fluid Film or Boeshield also work. LPS-3 for longer term. Real long term storage in barn consider cosmoline. Definitely take the time to cover the machine with a cloth tarp or proper machinery cover. This will diminish the rust and dust.
Also, if there are animals sharing the barn with the Bridgeport, make sure its well ventilated with roof vents to release the ammonia vapors from their excrement.