Progress bar for ejecting USB flash drive?

OS is Debian 10. File manager is Thunar. I've noticed that when I copy a few dozen gigabytes to my USB flash drive, the process only takes a minute or two. Then when I go to eject, the ejection process can take an hour or more. The USB drive is fine, it's just a lot of data to flush from the disk cache. The issue is this: I have no clue how much time is left on the ejection process. There **must** be a way to see the progress on this. Or better yet, is there a way to copy files to a USB flash drive and skip the disk cache entirely, just for that physical device? I know how to skip the disk cache for dd, but that is useless here. And of course, sync has no progress bar and as far as I know doesn't allow you specify a physical device.