Lay down an old sheet at the foot of the dirty wall, so that moisture doesn't flood the floor.
Put on dish-washing gloves. Mix ammonia and water in equal parts in a bucket.
Soak a large sponge in the diluted ammonia. Use a ladder to access the top of the wall, then wipe your way down the wall, using vigorous rubbing motions while moving down the ladder. Work your way across the wall until the cigarette-smoke stains are no longer visible. For particularly strong stains, use undiluted ammonia.
Rinse the sponge in clean water and go over the wall again to remove the ammonia smell. Dry the wall with the sheet.
Repeat for remaining dirty walls.