I did half of a twosided mold using Smooth On Mold Star and used clay I thought to be non-sulfur. It seems that everywhere the clay touched, it didn't set. It was sticky on the surface, so I took a razor and cut the surface off and intend to redo the registration keys and surface of the mold. However, the surface of the prop itself is covered in goop which I assume will screw up the possibility of it molding properly. I want to clean this off and then spray with acrylic paint to seal it. I spent a half hour in the shower with liquid dish soap scrubbing the mold after cutting the sticky section and the prop, but it still has uncured silicone on it. How can I remove it in a way that will permit the next layer of silicone to cure?