Rules needed
1. Disconnect test devices from ALL networks and disable devices for connectivity
2. Plug into powered USB hub to protect PC from power shorts & other physical mischief
3. Plug USB hub into Linux VM with no permissions for user to auto mount, execute etc
4. Don't execute any executable files EVER
5. Open files with basic text editors or other program that will not run any RICH media (aka potentially nasty active content)
6. Format drive, including boot information, preferably taking account wear smoothing and other file fragments
7. Re-use if brave or trash if sensible - I don't know how to be absolutely certain that there is no in-built chippery or hardware modification that would not normally be present.