If you just want to do Leahanmore on its own then park at 015135 J (lots of space). Walk about 400m up the road westwards and a rough track goes right to a bridge over the river. There is a gate through the deer fence just beyond, then open tussockland leads up over Leahanbeg to the main summit. Higher up rocky slabs provide a bit of easier going, and low down the remains of an ATV track up the west flank of the valley give a bit of help, but most of it is just plain rough. The view northwards to the main Derryveagh range is excellent. Linkback: https://mountainviews.ie/summit/645/comment/20076/