What other practical methods can we use to help addicted gamblers become better asides professional help?
Rather using mere words and advice to try to talk and addict out of his habit, I think there are way more practical methods to use, because I don't believe talking is to the person and trying to convince him or make him see how harmful gambling addiction is isn't practical enough/at all because when a person is addicted, I believe he already knows that it has negative effects on him so reminding him what he already knows wouldn't be so much good and idea in helping him break free from the addiction.
Rather than using the talking method, you can try other things, but first the person in question must first realize how much he needs the help you're trying to offer to him before he can be able to comply with you to help him, because there's no way you can help a person change from a habit when the person in question doesn't even see anything wrong in what he's doing, you'll simply be talking on dead ears or trying to communicate with a blind man using sign language.
There was a story I heard about an addicted fellow who's relatives took the bold step of going to every gambling outlets and casinos to blacklist the fellow's name so he can never access any of their services, online or offline, I think this is a more practical way to help such a person.