Could aircraft suppress a harbour's anti-aircraft guns?

Could fast aircraft use rockets or gunfire to suppress anti-aircraft weapons during a harbour strike?

Yes, especially against exposed gun positions, if enemy fighters did not break up the attack; a modified Fulmar or Firefly could support torpedo bombers that way.

Mosquitoes or Beaufighters armed with rockets could attack ships and harbour defences, but success would depend on reaching the target without enemy fighters breaking up the formation. Suppressing exposed anti-aircraft positions is more plausible than trying to duplicate a cruiser broadside from the air. A modified Fulmar or a Firefly could perform that supporting role. Torpedo aircraft would remain responsible for the main attack on the ships.