The popular descent from Binn Idir is to Mam Ochoige, and is very tricky, as any guide book or commenter here tells you. On a recent trip to Binn Idir I took the direct route off the mountain down to Derryvoreada, heading just west of south from the summit and aiming roughly for the school that sits in isolation in the valley at L881 511 G. This route wasn't recommended in any guide books I had consulted, but looked doable, and was. Later, I made the ascent from the same spot, parking across the road from the school. It's not a good spot for parking, and I'd recommend using one of the other laybys along the road. But the ascent from here is straightforward: Binn Idir is on the right as you look up from ths site, Binn Caoinaigh on the left. Ascent to Binn Idir is direct and steep with some false summits, and some lightish scrambling required, but with no major obstacles or navigational difficulties (on a clear day). It's also more sheltered from prevailing wind and rain than the Mam Ochoige route, or has been on all days I've been in the area.

For those taking the classic route from Mamean to Binn Caoinaigh to Binn Idir the descent from the latter to Derryvoreada leaves a shorter road walk back to the carpark at Mamean and also avoids the long trudge across bog that the Mam Ochoige descent requires. Linkback: https://mountainviews.ie/summit/108/comment/15245/