For a few days my short-haired cat has been trying to cough up a hair ball. He's a new cat from the shelter and his coat wasn't in great condition when he came to us, but it's getting better. We brush him several times a day. He still hasn't coughed up the hairball, and he seems to be trying more often but the effort seems a bit weaker each time. I got Petromalt and started using it yesterday. Anything else I can do for the poor guy? How long should I wait for this medication to work? Any other suggestions? Thanks.