If your object already has a hole in it, try filling it with hot glue (letting it dry) and then sanding down any rough edges. Otherwise, try using silicone caulk. However, be sure to choose an item that isn't broken beyond repair. For instance; if you have a cracked bowl, choose one from a thrift store that is still intact. (Such bowls are better for painting – because they offer more detail and angles to work with, rather than being smooth.)