You have to die about 20 times in one playthrough of a mission to get this trophy. If you plan on going for the Veteran trophies you shouldn't need to try to get this as you'll get it during that grind. But if you happen to be some kind of Call of Duty god or simply don't want to go through that Hell, the best method in my opinion would be to just cook grenades in your hand until they explode. Do it 20ish times and you'll unlock the trophy.