Knockbrack is quite easy to get to, but not so easy to explain :) I assume you have the OS map? Coming out of Tullow, head towards Enniscorthy, turning left at the junction with the main road. Go over Ballon hill and turn right at the Forge restaurant. Follow that road until you come to a Y junction and turn left. Take the next right turn and head uphill until you see a brand new bungalow on the right (no-one had moved in when I was there), there's some restored granite farm buildings across on the left.

Park around there somewhere and head uphill from behind that house. From there I'm a bit hazy cos I wandered around a bit looking for it. You could really do with a gps because it's almost in a corner between two fields, even with a gps I got in a muddle! Your best bet is to print off the map on archaeology.ie.

That Rathgeran stone is a little easier, in Ballymurphy head in the direction of the more famous Rathgeran stone but just before you leave the village take the right turn uphill signposted 'Rathgeran'. Go up that road and turn left at the T junction. Follow that road around until you see a farm entrance on the right, a long driveway up to the farmhouse. Ask there, the stone is through the field entrance to the left of the house, head across the field to your right to the corner jutting out into the field. The stone forms part of that corner.