I like it. smear more mud and sand mix on it, make if finer for the render. If I'm not mistaken render is the same as plaster just used on the exterior, maybe Teresa would research that. Any line stone near by? I tried cooking clam shells once on a brush fire to make a rude lime putty, but it wasn't as successful as I had expected, a line wash could help with longevity of the material. Not sure how to salvage for that other than making it from fired limestone, cool science project though. Not sure maybe some kind of oil coating on the mud, again research.