Today I unlocked it alone since I just recently gotten an xbox one and don't really need a second controller for a while. I used the infinite ammo skull and the boom skull. Although prior to starting the mission it states that achievements will not be recorded while using the bandana skull, I tested it out myself and received this achievement by simply throwing hundreds of grenades and ducking in cover, it was simple for me despite it being on legendary .
I ALSO USED THIS METHOD ON HEROIC FOR NOT USING A MED KIT FOR THE ENTIRE LEVEL FOR A SEPARATE ACHIEVEMENT. I received my achievement with both cases