Go to Munmak on highway 50. After the toll gate take your first right. There are signs all the way there after that. When u come to Ganhyun town (little), drive to the end of the township and then under a bridge (very small and tight tunnel under the bridge). As soon as you come out you will dive 40m and see a large car park and a toll gate entry arm to access the large car parking area on your right. Take the ticket and enter this, driving to the shops on the right. Follow that road all the way through, over a ford crossing. Basicly keep going as far as you can until you come to a Minbak area where the river is on your right, a large crag to your right that is accessed by a wooden footbridge. From the toll gate I am guessing it 20 mins to the car park where you enter, and then another 5 mins to the crag. Hope this was of some help.
I am 90% in.