This is very easy.
I did on OPERATION A - MISSION 1 . Because in my opinion is the easier and very quick.
Ok, while chossing ur weapons , on the right side of the screen u can active the two skulls.
I recommend to you:
Blind (EXP x 2): Vital HUD elements are hidden
Famine (EXP x 1.5): Dropped weapons have much less ammo
During the mission , the skulls will not create too much trouble. Because the mission has few enemies and a lot of ammo from your start loudout.
I used the AR( assault rifle) the whole mission and had no problem.