I use a flywheel knocker. It is hollow about half way down and has soft brass at the very bottom, this way you dont knick up the edge of your crankshaft. You just lightly hit it with a hammer and the flywheel pops loose. You can pick one up at your lawnmower shop (or online) for about $3.
My father recently inherited one that must have a head in excess of 5 lbs, plus the steel handle. In most cases you just pick it up and let gravity do the work.