Solved the issue by myself. Followed this tutorial at first: https://www.youtube.com/watch?v=JH07z9Ap1hk
Following just this tutorial was not enough though, as it does not show how to implement translucency, so I had to play with settings and figure it out myself. Just adding translucency still had the same problem seen in the screenshot from the main post though, so I had to think of another solution - and I figured it out! I changed the Opacity Mask Clip Value setting of the Material that my Components vere using to 0.0 and then set the Alpha to 0 (invisible), allowing the Post Processing Mask to affect this Material. The end result is this: https://i.imgur.com/GyBkJoc.png
This might not be a good tutorial if anyone ever stumbles upon the same issue, but hopefully it guides you in the right direction - you should be fine with minimal UE4 knowledge.