On my 2015 crossing I ‘discovered’ a shortcut through the Midhill Windfarm that doesn’t appear on the maps that may be of interest to some.

From the end of the forestry track around Tipperweir where it intersects the ‘Builg’, NO 691 863, head south along the path for 150m to the wind farm track & then follow track north east to pick up old forestry track, NO 702 871, down into North Dennetys. I reckon it saved an hour over heading north over Kerloch, though if it's a nice day Kerloch is worth a visit.

You can find a map of the windfarm at:
http://www.gov.scot/Resource/0043/00436922.pdf

In the same general area as PaulA's above short cut, those aiming to exit the forest by the Builg Road at NO719830 to Corsebauld will find the track fork at NO718835 impenetrable. However if the contouring track is followed round to NO722835 another track exiting by a gate at NO723830 (by an OK camp spot) is clear. TGOC Final Details have for years warned that both of these exits are blocked, but the latter was fine in 2015.

The path continues down through Corsebauld Farm (accessible but not friendly) past a hoard of abandoned vehicles.

Why short cut? The Fetteresso can be lovely and has some decent camping in it as well. I use the weigh man route which continues on the forest tracks as far East as it is possible to do!