I wipe them out with alcohol after casting and store them in a dry tool chest. Before using again I clean them again with alcohol and then spray them with a graphite mold release. I have cast iron, steel and aluminum molds and I treat them all the same way for the last 45 years with no problems whatsoever.
No special care for my Lee molds, I keep them in their original boxes and store in a plastic tub w/top. I just spray them with brake clean before casting. My iron/steel molds get a shot of Kroil if they aren't gonna be used for a while and a good cleaning with brake clean prior to use.