Hopefully, your brass ports
are actually Bronze.
Sometimes the following work on Bronze:
Lemmon Juice + Salt
Baking Soda + Vinegar (Rinse well after)
OOPS, just about forgot:
After cleaning, I like to put a little "Zip" wax on port lights. Helps protect the sparkle. (Zip is the cheap
car wax, you just add to wash water
- any wax will do, but this is quick & easy)
Lotsa luck, I'm certain they'l sparkle when done!