Big W on a Stick

Assuming the gates locked you'll have to park the car near the golf club and run down the gravel road about 1km (if not locked drive in and knock 2km off the run). Once at the carpark at the end of the end of the road look for the trail sign and take the track down to the swingbridge 500m away (spraying your shoes at the dieback station of course on the way). Cross the bridge turn left and a few hundred metres up the track there's a right hand turn onto Upper Kauri Track (a maori carving stands there just up the track).
Climb up Upper Kauri track for 2-3km to a junction (Long Rd Tk) and turn right and follow the undulating Long Road track past the junction with Smyth Ridge Tk and onto the junction with Wainamu Bush Tk on your left (if you get to Lower Kauri Tk you've gone a little too far). Head down Wainamu Bush track for almost 2km where you'll cross Wainamu Stream and track a little along the stream in a cool valley till you see the track further along on the other side. From here the track meanders its way uphill to Wainamu Junction (you can take a short 1km or so diversion here to the Kuataika Trig which provides a great view over the Waitakere's to the coast - take Kuataika Track and look out for the short side track to the trig on your right if you want the view). Otherwise at the junction turn back onto Smyth Ridge Track and after a short downhill, climb your way up to the junction (on your right) with Sisam Tk. This ones a little technical rooty beauty that's hard yakka to get any pace on. Near the end this puppy drops steeply into Smyth Stream where you are at the top of a very narrow valley and waterfall (take care if you dare have a closer inspection because you are at the top of a long drop from here).
On the other side of the stream is Simla Track where you make up for all that steep down you just did in an equally steep up. Burn the legs by all means because its a short steep dig up and then more moderate gradient thereafter back to the top and a junction with Ridge Road track where you turn left.
Take this track to a junction at a small clearing (Simla) with FenceLine Tk and Long Road Tk. Take Long Road Tk (feels like an extension of the track you were just on) and follow this undulating track using the little side diversions marked Montana trail that avoid the steepest, slippery sections of Long Rd (they all are short side tracks that bring you quickly back to Long Road Tk.) Follow this to the junction with Upper Kauri Tk and retrace your footsteps back to the car.
Note : there are untold ways to lengthen this run so take a map and take you pick in terms of distance and terrain as its good country up here. My favourite extension is at Simla turn right down Fenceline Tk to Waitakere Dam and cross the Dam and just up the access road 100-200m you'll see a track on your left and stairs (Waitakere Tramline Walk). You can take this and then Anderson Tk to get back to the car also with a few extra km's.