Distance: 3.5 km (2.3 DOC hours) - Unmarked route, clear - Hard terrain
Altitude: 65m to 787m. Gain: 783m. Loss: 62m . Gradient: 14 deg (Moderate-hard)
Skills:

Unmarked route, clear (7/9)
Unmarked route, follows obvious geography (river, spur, trail, etc)

Secondary, unmapped (4/5)
Route not on maps, an alternative recognised access to hut or along range / catchment

Moderate-hard (difficulty: 4/5)
Continuous moderate climbs

Hard (difficulty: 5/5)
Thick scrub-bash / continuous river boulders, waterfalls, or gorges

None (difficulty: 1/7)
No alpine skills required

None (difficulty: 1/6)
No unbridged river crossings

Unknown (difficulty: 0/7)
Not specified

From the mill site, bash through thick supplejack straight up towards 590 (1 hour). Travel gets better and more open on the spurlets leading to the spur from 590 down to the forks. Just below 590 (around 500), a reasonable trail is joined.
Carry on up the ridge to 708 (35 mins) and ensure you turn right (SE) to go towards Waitewaiwae. The trail is fairly well marked.
Just prior to the top, there is a small series of bumps, one of which has a few extra permolat tags on the trees. This is the start of the ridge down to Thompson (It feels wrong, but it is the route).

Note: Described in the reverse direction to your journey

From the junction, head down the ridge towards 708. Take care to turn left here and head down to 590. The track is fairly well marked,