I used a bo (6 foot staffs) or something long and heavy. With bo, you can use both hands. bokken tends to be right handed; although, nobody said you couldn't use it left handed. If you use bokken then get something big and heavy, like a suburito or just use a boat oar would work too.
or a burito in each hand.
Also, don't just swinging it at the air, try hit something hard like a log or a car tire, give you good feedback. almost forgot one more important thing, cut with your body, not just the arms.
Besides cutting, try tski a tree or a wall. if the butt-end hit you in the gut, then you have not extend enough. Saw videos of Chen taiji long pole exercise, looked very interesting. Planning to try that to see how it work.