How to safely remove a USB device from 2008 Core server?

I have a Hyper-V Core server 2008 that I administer via command line and remote tools. We have now got a new backup system in place and it involves me connecting an External USB drive (G:) to backup system state files. My question is how should I safely remove the drive for its weekly offsite swap?

I've tried using the devcon tool however it just says the 'removal failed with no devices removed' with no other explanation. I have noticed that there isnt a readily available x64 version of devcon and that might be the cause of the problem. (I have read of people downloading a amd64 version but I have not located it myself, if someone knows where it is please let me know).

The devcon command worked on my old 2003 x86 server with the command: devcon remove 3200AVJ_EXTERNAL

I have also looked at using fsutil volume dismount g: but it doesn't seem to work as G: is still listed as a connected volume.

I have checked that the volume is not in use via remote tools and the net file command. Both show no open files in the G:\ volume. This could be a decent substitute as it might be used to flush any remaining IO to the volume can anyone clarify?

Thanks in advance.