This route takes in Dooish itself and the South West top and took me approximately 3 hours, although that was at a leisurely pace. My track appears to start about 100m from road because I neglected to start recording. There is parking for probably 4-5 cars by the side of the road. Proceed south across the marshy/heather-covered ground for about 600m, where the ground begins to rise steeply. The hillside is also heather-covered, but becomes easier to traverse as you gain height. The views also improve dramatically with altitude, Errigal & Lough Altan revealing themselves.
At about 400m ascent, the terrain becomes increasingly boulder-strewn and a bit of scrambling may be required in parts. Rather than approach the very steep final part directly from the south, I swung around to the east and made the final push for Dooish up a mixture of grass & rocks, reaching the large cairn after about 1 hour 20 minutes. Tremendous views of the entire area, with Muckish & the Aghlas to the NE and Errigal directly west.
From there proceeded west for 1.5km over easy ground to the SW top, with a few up & down sections in between. The lesser top is also marked by a cairn, albeit an appropriately smaller one. It being a stunning summer's day, I lingered here for perhaps 20-30 minutes, which accounted for the 3-hour walk time.
I then descended directly north down the slope, which was steep in parts and required caution, taking me back to the R251, which left me with a road walk of almost 2km, but after the final boggy traverse (even in summer), it was welcome.