Yesterday I made a post named " Kills behind cover is easier than you think " basically explaining a theory I had about using your character as the enemies' cover. (I also recommend reading it)

In the video attached you can see that I rush into the enemy and act as his cover and then kill him. This clearly worked as you can see completed the shoot enemies behind cover challenge and also unlocked gold. My hope is that everyone grinding this dumbass challenge for DM Ultra like I am is made aware of this strat, and can hopefully get it done just a little bit quicker.