We live in a house that's over 100 years old. The walls in the old coal room in the basement have been flaking off for years and recently I noticed mildew on them. My husband and I chipped off most of the cement and are now using mortar to resufrace the wall. Is this going to work? And how do we get a smooth finish on the walls? We just use the room for storage, but would still like a nice smooth finish. Thanks for any info you can give me.