You can park on the road towards Pontlottyn, on the edge of the closed lane that takes you to Cefn y Brithdir by foot. There is also parking if you turn left and head down towards the small pond.

Beacons View
If you go to Flickr and zoom in you’ll see the road and where my white car is parked. | Tamron Adaptall SP 24-48 @ 24mm, f11.

The walk is easy if you follow the road, or you can take a shorter route on the way up like I did that takes you up a couple of steep parts but reduces the time you spend ascending. 

Cefn y Brithdir
The road skirts around the edge of the main ascent, but you can follow trails straight up it. The high point is still some way beyond this steep part though. | Tamron Adaptall SP 24-48 @ 24mm, f11.

You get good views of Pen Garnbugail to the West and you can see the Brecon Beacons horseshoe and Cefn yr Ystrad looking North. The hill is pretty clean overall, with minimal fly-tipping (which seems an odd thing to celebrate, but some valleys hills are covered in fly-tipping) and is a pleasant walk to tick off another Caerphilly hill.

Valleys View
Pen Garnbugail is to the left and along the ridgeway, just in picture on the left is Mynydd Fochriw. To the right is Twn y Waun. | Tamron Adaptall SP 24-48 @ 24mm, f11.

The summit is not marked in any way, so I just walked using my GPS and OS map to stand at the spot indicated.

Cefn y Brithdir
The highest point is to the left of the trees and up the small bank. | Tamron Adaptall SP 24-48 @ 24mm, f11.

At least it is open and grassy so there is no need to fight through thick heather or other plantlife. I walked back via the road for a little bit of variety.

Cefn y Brithdir
Cefn y Brithdir looking North. | Tamron Adaptall SP 24-48 @ 24mm, f11.
Cefn y Brithdir
Cefn y Brithdir looking South. | Tamron Adaptall SP 24-48 @ 24mm, f11.
Beacons View
The road back to the car. | Tamron Adaptall SP 24-48 @ 24mm, f11.