Just done a forum search for the same info as the OP! (assuming youre not the same John as I was out there with!)
I have been up there a few times – there are some good rideable tracks – mostly double track and some old deteriorated tarmac road. There is a also the odd bit of more interesting track in the woods around Comrie – but short and difficult to fit into a bigger loop. Unfortunately what is shown as s/t on the 50K map is not. You can loop in with some good and scenic riding out Glen Artney and FIndhu Glen (tho I have heard that some of the locals are less than welcoming so be prepared with your charm!)
Scenery is terrific and Comrie Croft is worth a visit if you are in the area.
There are new tracks above Braefordie – with all the character that new tracks have – but its still out there and I'm also curious about a possible descent off Ben Chonzie across Carn Chois to W of Turret
The circuit of Choinneachain to E of Turret is steep landy track (a long hard push for most) with a rough track descent. Nice views and good miles but nowt technical.
Comrie & over to Ardeonaig is OK to tick off – its tarmac to the far end of Lednock reservoir – we found no sign of the marked track so there was the heather hag push carry to the shoulder and a nice but short descent to the loch.
Again on the return through Almond there is (or was) no sign of the marked track. This bit I have done several times c/w and a/cw and found the best way is to push up the steep track from the dam to were it says Dundornie on the map – though what looks like a flattish push carry on the map is still v difficult!