The silver plate is really heavily tarnished, but not smooth/blue-gray-purple/iridescent -- it's nubby/rough and dark gray.
Normal polishing methods (tried Tarn-X sulfur-ish liquid, Tarnishield, and Mother's) are taking forever.
Anybody encountered something like this? Here's the tuba in question. Notice the pebbly texture on the bell stack -- that is what I am having trouble getting smooth and shiny.
![Image](https://i.imgur.com/l2a03gr.jpg)