I use blue silicone grease inside my fixed spool reels.Truly waterproof. The trick is to not use too much.Just a thin smudge regularly will suffice... makes cleaning a whole lot easier when you next service your reel.
CRC Inox Tackleguard or WD40 (there's heaps of products)for the outside and I can also recommend a product called "SALT AWAY"... great for melting salt deposits off rods reels outboards wetsuits boats quads etc. I use it and have found it a top product.