Shielding equals insurance. No amount of shielding will make a single coil not hum, but it can make it hum less. It's preference, but IMO shielding the control cavity is more important than shielding pickup cavities, especially with humbuckers that have shielded cables. Too many times a pickup cavity has copper tape or shielding paint but the shielding isn't electrically continuous with the ground of the system. It's easiest on a top routed strat, but on a rear routed guitar that has holes drilled from pickup cavity to control cavity, unless the channels are shielded, or there is a ground wire connecting the cavities, or there is a jumper from the pickup's ground in the cavity, it can makes things worse than if not shielded at all. The whole point of shielding is to allow the interference a path to ground.
