Up the red route properly- ie past freeride, down Pennel’s Vennel, then up the red climb to the top. Not the fastest or the easist but the most interesting IMO.
I strongly agree. Pennels Vennel is a great bit of trail and taking the singletrack climbs is far nicer that slogging up fire roads purely to get to Spooky Wood a bit quicker.
The route by Anderson Road and the route glupton suggests both involve particularly grim fire road climbs.
A 120mm travel hardtail is easily capable of giving you lots of fun on the Glentress red. A full sus will give you lots of fun, too, though a burly one may add more effort to the climbs than fun to the descents. It’s all down to taste. I can have a blast there on my Chameleon (hardtail with 140mm forks) or on my (140mm travel) full sus, or on my 100mm travel full sus, for that matter, though they all make it fun in slightly different ways. 🙂