I haven't messed with an SC balancer, yet... But on other cars to keep the engine from turning over I remember hole or slots, maybe through one of the pulley bolts that you could stick a screwdriver in the hole and if you're lucky it would catch against the block or something solid to keep it from turning.
Or maybe get some good leverage like a breaker bar and try giving sharp yanks instead of just pulling steady.
Have just a little more patience and you'll get more specific answers from someone here who knows exactly what to do. You'll end up a lot happier doing yourself. Everytime I take something to someone they screw it up or something else goes wrong. Even if you end up having to buy a tool or two to do this chances are you will still be way ahead of taking it to someone. Just my $.02