Take a chopstick

Take your prop

Put it on yore chopstick

spin it around on the chopstick

Put the chopstick over a crate wide enugh to let the prop spin, but short enough tolet the two ends of the chopstick touch the ends of the crate (I use my dad's beer box)

Then you balance the prop on the chopstick so that the prop is // to the ground

let go if it spins to one side its heavy on that side.