This is a route that I can happily recommend... well the first 3/4 of it anyway!! With two cars it can be significantly shortened, I will give the reasons why I wouldn't cut the first part, but would cut the last!
The first section 6km/1 hour starts off on not unpleasant forestry tracks and a very quiet and scenic road. I found that a lot of the forestry tracks that show up on the OSi map are not actually there, but still managed to negotiate the forest without having to back track. In early autumn the colours on the hillside as you walk the road to the bottom of Ballinacor were beautiful. This stretch is a good warm up before starting the first real ascent of the day.
I choose a direct trackless approach to the top of Ballinacor, going through heather and high ferns. I suspect that there might be a better track to the left of my approach, following the right hand side of the Ballycreen Brook to near it's source before heading for the top from the west. From the top of Ballinacor I dropped down the far side, again through rough ground, before joining a well defined mountain track. From this point until Fananieren it is a very pleasant walk on good terrain and gentle slopes, and well defined mountain track, going in a horseshoe route above the valley, although by the looks of it, some of it could be very boggy at a wetter time of year.
Fananierin turned out to be a surprising highlight of this walk, with great views back to Croaghanmoira, into the Ballinacor estate, Drumgoff barracks and up the Glenmalure glacial valley. From the summit, this route then backtracks on itself for a small distance before turning right, one fence crossing before walking down the field to the gate and back out onto the Drumgoff to Aghavannagh road.
If you have a second car, this is where I would recommend parking it (near T10187 89257). As the last part of this route is along ugly forestry track, through a forest break and road, it does take you over the true summit of the horrible little **** of a hill that is Slieve Maan though. A hill that I will not be revisiting.
In summary, great walk apart form the last stretch!