When a weapon is introduced, students get very attached to using it, or, conversely, they can't use it at all. Moving naturally and using the weapon fluidly during the technique is a goal that many miss. The weapon is an inanimate object. With no attachment to being useful or even who wields it. The same way one makes use of the earth, or the wind is how a weapon should be considered.
But something more. Beyond common sense there is uncommon sense or things that can't be understood with the intellect. This is hi jo shiki.
I was at a class in Noda one day when Hatsumi Sensei said:
Don't show or use your knife right away. Animals bare their fangs. Humans don't have to show our fangs. We smile as we defeat you.There are many ideas contained in this quote. One is that when someone has a knife in their hand, both they and their opponent's attention tends to be on the knife. As if the knife captured their minds. The inanimate piece of metal can become a trap for those who allow it.
Another idea Soke may have been referring to is that in ninjutsu, that which defeats the adversary is often hidden. It can be hidden in plain sight. A hidden weapon, or strategy. A subtle control of space or psychology that is never seen.
And smiling as we defeat you could be describing a purity of heart that is unmoved by insults or threats. Unattached to the outcome of the exchange. Just moving naturally as needed. A clear heart has nothing to prove.
Don't try to use your weapon expertly. Add some Hi jo shiki.