This is an easy walk starting from the large carpark at W34900 86100 A and following the track (which is show as part of the Dulhallow way on the Discovery map) past bog works along the access road to Seefins mast covered summit. There are interesting views south to others of the Boggeraghs. The summit itself has telecoms towers with very scruffy ancillary equipment, and, unusually, a rotatable amateur radio aerial which is controlled remotely.

If you are worried about the no access signs then make a bee-line from the car-park along the line of a fence to the 486m spot height and on to Seefin itself. There is a track indicating that others have taken this route before.

An alternative approach, and one that gives access to the East top, is to park at W37314 87049 B where there is room for multiple cars. Head west along track for about 200m to a crossroads of sorts, turn left and follow good track south-west then west for about 1.2km until you reach W36256 86328 C, where you'll see a rough, grassy/boggy track running NW. This eventually becomes single file, but continues all the way to the summit. There are three cairns of sorts, all of different sizes, but the high point is actually a large grassy mound 20m south of these. Allow roughly 45 minutes up and down. Linkback: https://mountainviews.ie/summit/483/comment/5242/

My cold, wet and misty ascent from the car park between Seefin and Musheramore (349 861 A) didn't really add any information that pdtempan hasn't already given: yes, there are private road signs on the route that seems obvious from the map, yes you can follow the fence over pt 486m (it's occasionally boggy, usually tough going, the usual drill) and the summit is ravaged by assorted high frequency transmitting stuff: definitely a top for the bagger and no-one else. I'm posting simply because just after leaving the car park I came across a fly-tipped jet ski, and I can conclusively say that's the first one I've seen in over 25 years of hillwalking. You have to love Ireland. Oh, and my casual navigation on the way down led to a rather embarrassing reascent to get back to the car, accompanied by distant disembodied laughter from the direction of Fenit. Linkback: https://mountainviews.ie/summit/483/comment/3514/

One wonders as you traverse the country what made Fionn mac Cumhaill so tired that he was constantly sitting down. Fionn seems to have travelled the country trying to find high points on which to park his posterior. Given the choice between Musheramore and Seefin, there doesn't appear to be any reason for Fionn to sit at the top of Seefin other than pure laziness.
The access restriction signs appear to have disappeared from the private road, but I'd still prefer the walk up the line of the fence (there has to be some challenge).
This appears to be a popular place for turf , though I suspect the days of turf harvesting in Ireland are numbered with the bog ecosystem disappearing fast around the country. Linkback: https://mountainviews.ie/summit/483/comment/6755/