Jukendo: Front Hand Grip (銃剣道: 基本)

Stand holding the mokuju vertically in front of you with your left hand.
Your hand should be straight, no bent wrist.
Lower your arm without bending it until your right hand can grip the butt.
Pull the mokuju in to kamae without changing your front wrist grip at all (no releasing the two fleshy pads of your hand from the mokuju).
Keep your front elbow in the same plane in front of you.
This should result, if you have maintained hanmi (sideways stance of the body), in a very small area of the kata being visible to the opponent.

If, like me, this is impossible due to

• New kata being stiff
• Wrists being designed for hauling nets from the sea rather than elegant movement
• General ineptitude

The best solution is to find a passing sensei and ask, politely of course, him to poke you in the ribs any time he sees it open. If you are averse to this volume of beatings I guess you could do footwork practice in front of a mirror and look for the opening. Personally I find the beatig method teaches me quicker.