Limiting doesn't really help at all because they could just cheat on their own.
Limiting funds may not bring effects to addicted gamblers, but it can be one of the ways to prevent addiction. Moreover, this way can avoid us from playing excessively in gambling and also prevent debt/loan.
The best way is to seek help from family and friends
I agree that family or close friends who can help an addicted gambler. Those people know more than others. They have a higher chance to make the gambler to recover from addiction. But sometimes, they also need experts or professionals of mental health as the OP said.
Wanting to recover from gambling addiction truly needs sheer determination and will power from the gambler. In the end, it is him that will determine the total withdrawal from this game. But yes, support groups are needed to help him not to go back again to his habit. They will serve as the reminder why he is doing such change of lifestyle and be on track to his goals.