My daughter and son-in-law bought a 50 year old house. The walls are all cement. The bathroom is guite small so they are trying to enlarge it by taking out the tub and putting in a shower. Over the tub was a lowered ceiling which they have taken out however the ceiling that is left is extremely rough. There is cement or hard plaster which is quite jagged in places. We are trying to figure out how we can refinish it so it is all smooth like the rest of the bathroom ceiling. Do you have any suggestions?