When you drive from Kuala Kubu Bharu to Fraser's Hill, you will see, just after the Selangor Reservoir, a side road leading to Kg Pertak. Follow this road,through the village and park your car where the road becomes bad. There is a footbridge across a small stream. Follow the trail until you reach the ramshackle bridge over the Sg Luit. Just after this bridge the trail forks, choose either one, they join again.
A few hundred meter after the Luit crossing there is a fork, where you keep left. The right trail leads to Bukit Kutu. Follow the trail along the river, you will pass an nice waterfall (Lata Jebus). After about 1.5 km there is another fork. Here you keep right, the left trail keeps following the Luit river.
You leave now the Sg Luit valley, and climb up the ridge between this river and Sg Rinting. Some steep stretches, but the trail is clear and well maintained by the Temuar for access to their gardens. Only a pity that it is also used by local bikers, so some parts are heavily eroded.
From the trail head it will take about 2 hours (6 km) to reach Lubuk Mecu. A huge pool invites you to take a refreshing bath. There is another fall just below Mecu, also with a nice pool. And Lata Medang is only 200 m further upstream. Keep to the left of Mecu, and you will find vague trails, or just trek the river, depending on the water flow. Do NOT take a trail to the left, just before you reach Mecu, it continues uphill and does not lead to Medang.
The Medang fall is quite impressive. To reach the upper tier, you must cross the river. This will not always be easy/possible, as the current can be strong! Be careful. And leave only footprints, these falls are still unspoilt, keep it that way
Here is a video of Lata Medang: