Empty the trash on a portable USB Stick.
Curb will either delete the trash on a USB drive or move it to your local trash. It has a nice interface if you traditionally launch the application, but for simplest use just drag your drive onto its icon, and it will work its magic and quit for you. You can choose to eject your USB stick when it's done, and to use Secure Remove if you have sensitive data (or are paranoid). This app does one thing and does it well.