Can\’t Empty Trash With Large Number of…: Apple Support Communities. Thanks ibcoleman. I haven’t had this happen, but I do know friends who have large numbers of files. Good to know.
In case anyone has this problem:
1) Open terminal window.
2) cd to the backupdb in the Trash folder on the external drive (i.e. ‘cd /Volumes//.Trashes/Backups.backupdb’)
3) Run rm as sudo to delete the files you can delete, passing the -v param so you can actually watch progress (as opposed to watching ‘Deleting -382,398 Files…’ Do this like `sudo rm -rfv Backups.backupdb/`
4) Go away for a very long time until it completes.
5) After completion, there should still be a lot of garbage still floating around, but these are mostly folders with odd characters in the folder name. But if you click on Empty Trash as you normally would, the remaining files should delete fairly quickly.
Looking back on this, the real issue is the bug in how Finder counts items in the Trash. It’s likely that if you just let the Empty Trash process procede, it will eventually finish. But once it goes into negative territory 99.999% of users are going to pull the plug.
The other benefit you get from just rm’ing the Trash is that the system doesn’t waste a massive amount of time (incorrectly) tallying up the number of files that it’s then going to delete anyway.