The best ways to make a cat use a scratching post are:
a. catnip (if you're cat is catnip sensitive).
b. Use a fishing rod sort of toy to play around the post and move the object at the end of the rod over the post. The cat will try to catch it and move its paws on the post. Almost always, that's all it takes to make them scratch it.
Taking the cat's paws and moving them on the post for her may work for some cats, but you run the risk of the cat taking an aversion to the post as most cats don't appreciate being manipulated like that.
I don't advise using the water pistol at all. It's a form of punishment and with 90% of the cats it's ineffective and can even make some cats afraid of the owners and aggressive towards them. Once the cat uses the scratching post, cover the places where she used to scratch with double sided tape or with a product called Sticky Paws (developed specifically for that - see this page: http://www.thecatsite.com/shop/claws.html
For more info about scratching posts and how to get your cat to use them see here:http://www.thecatsite.com/behavior/scratching.html