[rann]

Fair warning. YES indeed, Milliput (ultrafine white) does dry hard as a rock, smooths/cleans up with water (even cures underwater!) before it cures...but...

...as has been said, you must knead it THOROUGHLY for at least 5 minutes or it may not cure and will never dry. Five minutes seems like 5 hours sometimes. I've gotten impatient and have had this happen to me once or twice. Really enhanced my vocabulary...not in a good way!