How would you clean this?

How would you clean the middle chambers of this bong? I have tried everything from epsom salts to rubbing alcohol and just regular hot water and soap but nothing really gets the second chamber from the top and that bottom part of the main chamber. It’s annoying me so much. Any advice welcome!

How would you clean the middle chambers of this bong? I have tried everything from epsom salts to rubbing alcohol and just regular hot water and soap but nothing really gets the second chamber from the top and that bottom part of the main chamber. It’s annoying me so much. Any advice welcome!