I was migrating my files from my old MacBook Pro to External HDD1 when I learned this lesson:
Finder is not reliable for moving large or lots of file.
I was copying my iPhoto libraries and the progress was stuck at 80% for hours. I cancelled the operation and copied it using Forklift, and it is done way much faster.
For deleting bulk (and large) files, use OmniDiskSweeper. Don’t even rely on Finder for that.
Which will be moved back to my MacBook Air ↩