One place to start is from the public road at S9962 7318 A, west of the summit, where a forest track starts. Some have started further up this track from around T006 734 B. Another place to start is at T0172 7464 C. This route uses a pleasant stretch of the Wicklow Way of around 1600m to reach the base of the summit. The first part of Track 1325 shows a route through the forest using various tracks and open spaces to reach the top. Using this route keeps the walking almost entirely within the forest, however it requires attention to route selection as there are various false leads.
Talking to a farmer, the local pronunciation sounded like "Muskee" to my ear.
From the east it is possible to start at T02570 72524 D which is relatively near to Tinahely.

Muskeagh rewards on a good day with extensive views of South Wicklow. Muskeagh is part of a chain of summits leading south west from the main Wicklow mountains and is paralleled by an eastern chain including Croghan Kinsella and Annagh Hill all of which is very visible from Muskeagh Linkback: https://mountainviews.ie/summit/844/comment/5603/