I can't really recommend any alternatives, since the main route described is fairly direct and the easiest route I have found. However, below are the two other routes I have tried.
Over Creag an Lochain
Ascent : 1050m, distance : 15km
Start as in the main route, cross the bridge and through the gate in the fence-line. Now aim south-east, directly for the col between Cnoc Sgriodain and Creag an Lochain. This is a slog over tussocky ground. From the col, turn east and pick up a developing path to climb up Creag an Lochain. The path continues north from this minor top along the crest, meeting the contouring path at the next bealach. Continue to the summit as described in the main route.
From Crask Inn
Ascent : 1000m, distance : 21km
I'd been up Ben Klibreck from Vagastie a couple of times, then decided to try and find a different more enjoyable route. This wasn't it ! Just south of Crask Inn, a path heads east following the north bank of the River Tirry along Strath a'Chraisg. Continue along the path for 6km to Bealach Easach. I tried biking along this, but after persisting for a while, gave up and left my bike by the Allt Domhain. At the bealach, leave the path, cross the burn and head directly uphill on loose grass and heather clad steep ground. After the gradient easies, slog up the southern arm of Carn an Fheidh to Creag an Lochain and follow the route above to the summit on Meall nan Con. Return by the same route or following the Allt Domhain.