Take out the old filler, rinse it out in warm water and pat it dry. Then either use a syringe to fill it back up after putting it back in the cart or if you don't have a syringe, put it in the cart a little and drip 2-3 drops, push it in a little more and more drops, etc. You ALWAYS want you filler moist but not pooling. You can do this for probably about a week before the filler gets too beat up to continue using. Then you can buy empty carts to start the process over again or you can go to Wal-Mart and get a bag of polyester filler and make your own filler. Some members have also been using Lipton pyrimid (sp) tea bag material to use as filler and claim it is better than the poly fill.
Good Luck