its the top shelf at the oriental massage parlor. after a hearty massage she starts to play with your bung with her tongue. Then you rise up on all fours and she starts playing with your unit like its a trombone. Her face will then look rusty, hence the name. Its one of the common techniques taught in massage school.
Tyler won a couple grand in vegas and all he could think about was spending it at the massage parlor for a rusty trombone.