Took me a while to get back to this, sorry to everyone that gave me tips.
Here's the solution I ended up with.

Since I still didnt really grasp the snapshot/restore snapshot concept (yes I am kinda thick headed), I made a script to delete old files, starting from the link that Michael K provided, then proceeded to making a folder with todays date on the usb drive, pausing all active VMs (absolutely no need for 100% uptime here, company runs 9am-6pm), and copying all of /var/lib/libvirt in there, and then resume VMs and be happy.

Here is the script.

#!/bin/bash



find /mnt/usbexterno/backup* -maxdepth 0 -type d -mtime +15 -exec rm -rf {} ;



virsh list | sed '1,2d' | cut -d' ' -f3>/tmp/vmlist



VMLIST=$(cat /tmp/vmlist)

set -- $VMLIST

for i in $VMLIST

do

    /usr/bin/virsh suspend $1

shift

done



mkdir /mnt/usbexterno/`date +backup-%Y-%m-%d`

cp -Rv /var/lib/libvirt /mnt/usbexterno/`date +backup-%Y-%m-%d`



set -- $VMLIST

for i in $VMLIST

do

    /usr/bin/virsh resume $1

shift

done

rm /tmp/vmlist

If anybody has any tips on how I could improve this please be my guest :D