still can't polish brass - what am i doing wrong?

Is it actually solid brass? Put a magnet on it - if it sticks, it's brass-plated steel and scrubbing hard will take the plating off. If it's solid, a paste of salt, flour and white vinegar (equal parts) rubbed on, left 20 minutes, rinsed and buffed works well. Or ketchup, honestly. And check it isn't lacquered - plenty of brass is, and polish won't touch tarnish under a lacquer coat.