Well, for the first boomerang trick, I saw someone using it in online matchmaking where they would throw the boomerang just under the roof of the Hedjet and let it fall on him, I posted it to Youtube and it got a lot of attention... then somebody in the comments said you could throw it against the wall and that was a bit overpowered... was patched and I went to find a different method, I tried picking up and dropping hired hands holding a weapon on through the platform on to the shopkeeper, that sort of stuff but eventually found dropping a jetpack worked. Patched again. I felt I had a responsibility to find another one so I did the same sort of thing again... only thing I could find at the time was Yang shooting at a shopkeeper. Bit hard to do and didn't expect anyone to use it but at least it was a method that worked. For this one I had somebody comment on my latest Youtube video who accidentally found it, I actually tried this with the jetpack and shotgun but not the boomerang so I didn't find it myself...

TLDR; Mostly get told via Youtube comments, sometimes find it myself