szzuk - You didn't say how small the holes were. I found this while looking for something else in my computer and thought of your problem
https://www.microcut.ch/en/index.php
Another thing that works to finish the inside of holes, if they are large enough diameter is called 'ball burnishing' Basically you push a ball through the hole after lubricating the hole first. But the hole has to be large enough to be able to use a large enough rod to take the force of pushing.
https://www.microcut.ch/en/index.php
Another thing that works to finish the inside of holes, if they are large enough diameter is called 'ball burnishing' Basically you push a ball through the hole after lubricating the hole first. But the hole has to be large enough to be able to use a large enough rod to take the force of pushing.