been there, done that...
Some time ago I have developed a python script to exactly this task. It will not only create the address objects, but also address groups and super-groups to accommodate the group limits.
You can download it here: https://www.beneicke-edv.de/support/tools/#ext_blacklists
and use or adopt it to your needs freely.
The only requirement is that you have python installed. I might even make it an executable for convenience.
And no, there is no Youtube flic about this showing you how to run it :)
"Kernel panic: Aiee, killing interrupt handler!"