I had a lot of trouble completing both of those tasks,
controller – you need to kill someone flashed
grenadier – need to kill 12 pmc with grenades
Both of them are stupid quests, but now you can complete them fast.
Use the new and broken shotgun load 1 star ammo and 3 25 shrapnel rounds have some nades and go to factory (have the star the first in the chamber).
I'm almost at the Kappa container and had only 4 pmc kills the grenades 30 minutes in factory and I'm done.
For the controller one you just need to use the shotgun – flash and shoot the legs with shrapnel.
Most people running factory right now are running this shotgun so expect to be flashed back.