In case you didn't already know, the reason my portal gun is so accurate is because many of the parts were 3D printed. However, it doesn't mean it was a piece of cake to put together! The pieces I received in the mail were rough (to say the least).
The picture on the left is the back shell after I applied the first coat of primer, and the picture on the right is the final product
Let's just say between this shell and the front shell I used A LOT of primer (the shells absorbed it like a sponge!) And after a few coats I would go over it with progressively finer grit sandpaper. At the very end I was using 2000 grit wet/dry sandpaper (usually used for clear-coats on cars)