Not sure if this is the "proper" way but each year I soak all mine in warm water. Usually place a couple at a time in a large bowl - fill with warm/hot water - let sit, drain and repeat a couple of times. This seems to dissolve/loosen up any salting issues that normal washing didn't get. I then take it apart - removing side plates, handle and shaft, spool peice, etc. Let everything dry thoroughly. Once dry, I hit up every edge and moving peice/joint with some grease. At this point, I havent' physically removed any of the gears/cogs as I can grease the appropriate points without removing them. Once everything gets greased that needed greasin' - I put everything back together. Works like brand new. Smooth, etc.
Disclaimer - my spinner collection is by far not "top of the line". Most are basic reels from store bought combos but they work well for me and serve me well when taking buddies fishing. I've had a couple of my nicer (more expensive) reels serviced by a local reel repair guy during the "off season" because I don't trust myself - lol.