On arriving at the entrance to Raheenleagh Forest at T1529471417 A you will be confronted by security fences and signs giving notice of wind turbine construction, off-limits to the public.
However, I could imagine a scenario whereby you might choose to hop over a ditch adjacent to the barriers, and furtively walk up the forest track, hoping to avoid security personnel.
Using your GPS, you might then use those forest tracks to exit the forestry on its western edge and emerge onto open hillside.
There would (most likely) ensue a squelchy ascent, initially through clumps of gorse, until you reached the saddle with Croghan Kinsella. Google Map's Satellite View would suggest continuing over the saddle for a short distance, over a fence, and then climbing a gate on your right.
You'd walk on this track for a few minutes before taking a left turn which quickly brings you to the summit area.
You'd probably walk around the rough ground to the left of the track for a bit, attempting to ascertain the summit, but you might well decide that the highest point was the ditch to the left of the track.
Most likely, you'll retrace your steps, hoping to evade detection as you pass the construction works.
But I couldn't say for sure. I drove straight home. Trackback: https://mountainviews.ie/summit/1432/comment/18431/

Raheenleagh forest access being denied, decided to ascend from Carrig Woods on the west side but a tree felling operation put paid to those plans, so ended up at T11782 74968 B, just opposite a large bungalow, with electric gate and security camera. No one hereabout to ask re access so headed up a farm track for a short distance to a gate on the left. Crossed into field with electric fence and a few cattle. Avoiding the livestock and crossing three fields heading in the general direction of Croghan, passed by two small forests not visible on OS 62, and eventually met a really good track at T 11942 74029 C. This led uphill eventually beside a fence all the way to Croghan Kinsella. Now facing east headed down from Croghan to T 13605 73094 D, turned left here an a good forest track for a short distance to a T junction followed track up hill to right around Croghan East top. Just to the left of the track here is a small stony mound with some rottting old trees sticking out which I think is the highest point. Fantastic views in all Directions, this top has been replanted so get there soon for views. Trackback: https://mountainviews.ie/summit/1432/comment/18134/