What should I do if I forge the rust on the kitchen knife by hand?
You can use white vinegar. Put a little white vinegar on the kitchen knife first. It will be wiped with a cloth in a moment. Be careful not to hurt your hand. After cleaning, rinse with water and it will be ok. I have never used this method either. You can try. I read it in a book, so you don't have to bother too much. By the way, dry it, or it will rust next time.