Salt water slowly dripping inside a reel will wash away its lubricants. Parts will begin to squeak, corrode and stick. Nothing in fishing bugs me more than to finally get the big one on the end of my line, only to discover the reel TIm using doesn't work properly because someone forgot to take care of it. Don't power wash them or 'hit them with a jet from the hose, or you'll only push salt and moisture deeper into the reel.
Soap breaks down the crystalline structure of salt.
Once your reels are dry, give them a light spray with a protective oil like WD-40. All you want is a thin film on the reel. Regularly lubricate handles and any moving parts you can reach from the outside of the reel. Again, you're shooting for a thin film, not oil dripping all over the place. Don't lubricate the reel in places where the oil might get to the drag.