Little John,
Traditionally, brass instruments have been engraved with a flat graver using a technique known as wriggle tooling. If you check out this link you will see Jason DuMars using the technique on the bell of a saxaphone.
http://www.youtube.com/watch?v=s5OEDVrOtRg
Click on the link under may signature to go to my illustrated glossary where you can learn about terms like flat graver and wriggle tool.
Regards,
RB