Three of us completed a 2-day loop over the weekend, starting from Troopers Creek Campsite (a bookable 4WD camp 4km from Roses Gap). This is a good spot to book for a few nights, potentially for base camp/ first night and to leave the car there, potentially safely due to others likely to be there. Only $15pn. There is a GPT trailhead carpark about 500m up the road which would be another option.
The trail from Troopers Creek intersects GPT about 100m so from the start. Our route (which included an overnight stay) was:
Troopers Creek (quickly links with GPT for the "Waterfalls of Gar" section > opted to take the out/back trail to Briggs Bluff > continued GPT to Gar (Mt Difficult) GPT camp > continued on to Mt Difficult summit > back to Gar Campsite for water etc > continue GPT towards Werdug (above Wartook) > intersected with 'old' track that heads towards Longpoint East > looped back NW to Briggs Bluff intersection > returned on trail back down to Troopers Creek campsite.
I would rate the sections of GPT that were on our route as quite comparable to other non-GPT trails in and around the Northern Grampians. GPT was sometimes just basic track through the bush, but some of the rocky sections through passes and involving sharper climbs do include rock slabs forming sections of steps. Some of the non-GPT sections we were on are noticeably less trafficked and a slightly overgrown; maybe not a bad thing. Trail markers are far more prominent and consistent on the GPT sections, compared to non-GPT. Quite a few well positions cairns proved very helpful in staying on track. New GPT communal hut, private (LTO) huts, toilets etc at Gar were attractively designed and well positioned on a ridge with stunning views. We encountered numerous GPT campers doing the segments through to Halls Gap. Plus quite a few day walkers doing Briggs Bluff and/or Mt Difficult. We encountered no-one on the outer section of our route which was non-GPT. My sense is that GPT will attract traffic, but there are plenty of non-GPT trails that will remain quiet and undisturbed, with plenty opportunity for dispersed camping (albeit not permitted, as I understand it).