resurrecting an old thread here as it's my neck of the woods.
the above photo is looking down the Garrell Glen to Kilsyth unless i'm mistaken.
There is a path of sorts here - more of a farmer's quad track by the looks of it but as said above it is very wet and boggy although not in the same league as the man-eating terrors of the ground between cort ma law and leckett hill
You could start at Queenzieburn and go up via Birkenburn reservoir which is a better path as it was made with type 1 a few years ago to allow vehicles up to the reservoir (so I was told). Either way, it's 'all weather' now whereas previously it was grass with some heavy duty bog-trotting once up on top. Interested to try the route from Cort ma Law to Meikle Bin as once at the trig point there looks like faint paths heading over in the general direction which don't appear on the OS map. Same thing at Leckett hill (vague looking paths heading towards the Bin)