Benglenisky is a good choice of Twelve Ben if you only have the time or inclination to do one, and is easily approached from a minor road to the west.
At L75024990 B there is ample parking space on both sides of the road. We continued north along the road for a few minutes till we'd gone beyond the residue of farmed forestry. Stepping off the road, there's a level, but surprisingly wet section before the ground steepens. Plenty of rocky bands on the way up, but these are all easily bypassed.
As the slopes level out, there's a confusing plethora of cairns that could, in mist, be mistaken for the summit which lies a few hundred meters further east. The views from the summit are wonderful - the gnarled rocky wilderness of mountain to the east and the lough-speckled moorland stretching westwards to the ocean. Linkback: https://mountainviews.ie/summit/420/comment/5937/