Like Muppet said, re the timing - dawn, when it tends to be calmer, and I've read that kingies don't feed as much at night, so are hungry at dawn. From now on, in the Waitemata fringes and rocky shoreline, even right up to the head of the harbour once summer kicks in.
I've been trying the same land-based thing on the southern side of the bridge.
The main difference is that I'm using braid, and lighter leader.
You will need a lot of patience because you are waiting to intercept kingies on their patrols along the weed line, and need to be in the right place at the right time for baitfish bust ups. Some of the top fly exponents for kingies say there's no point roaming too much and casting endlessly, choose a good spot and observe as much as you cast. Some trips a kingie won't show up, some they will.
Most top water guys chasing kingies prefer stick baits to poppers. I've heard people say that poppers get a lot of chasers, but not as many takers as stick baits.
There are a few decent low-cost poppers with good hooks and split rings if you do go that direction, and two main types: The blooper types, such as Williamson Jet (I've got some of the smaller size) and i think the Halco Roosta (not too big); and the skittering ones. Of the latter, give the Strike Pro Lazerlite a try, though they are only 40g, so you may struggle for distance with your set up.
As Muppet alluded to, the key summer prey along the papa rock coasts up your way are going to be piper and mullet (both 'sprats' and grey). So keep that in mind when it comes to colour and size.