Since I was last at Ballymoyle a new network of mountain bike tracks have emerged and one of them goes very close to the summit. Most people take the track from the old derelict building - you could continue to do this and bits of this trail are passable, but other bits are a struggle.
Instead, and being mindful of mountain bikes (so perhaps do this early in the day when it is quiet), continue pass derelict building and take the next mountain bike track that goes right (south). Provide along there c. 400m. Its good if your watch has an elevation feature. Around the 280m mark, turn right and the trig is within 30m, following a gap through the trees. Its not the most obvious of paths, but you should notice recently trimmed branches and gorse. Useful to have a gps to hone in on trig if in doubt. The pic incorrectly shows the peak at 332m - it is actually 280m on the trusty EastWest Mapping map.
The screenshot excerpt I uploaded, the person symbol, is approximately where the derelict building is. You can continue to start from here, but much easier to follow the bike tracks - at a time when the bike tracks aren't in use. That track runs south past the summit. I didn't follow it to its conclusion but there is an obvious way to the summit from the south now too on this track. Linkback: https://mountainviews.ie/summit/972/comment/23179/