if its just very top surface corrosion, fine steel wool should take it off.. once it is, you'll be able to see if the bluing is damaged or gone from those areas. If it is, I would touch it up with a cold bluing kit.
If the corrosion is more severe, causing pitting of the slide, or anything similar, then I would get out the fine sandpaper and sand the whole slide down and reblue the whole thing.
After all is said and done, wipe it down with some rem-wipes or oiled cleaning cloth.. just a light light coat of something to protect it, especially since 24/7 in a leather holster in the kind of environment you have is rough on metal surfaces like that.
Then I would wipe it down and reapply the protective layer every month or so- depending on the weather and how quickly the humidity gets to it.