Having ridden Cadair Idris on Saturday, in perfect visibility, I missed the right turn at the sheep pens at Haffoty Gwastadfryn and followed the double track which I was already on, bearing slightly left here and continuing up bearing right all the while, pretty much following the contours round. When that track stops, it’s not immediately obvious that there is a path running across the moor to meet the Pony Path at the junction on the saddle. This involved me riding / pushing over the open moor, aiming at the junction and stile, which, due to good weather, I could see easily.
I’d suggest taking the right turn through the gate at the sheep pens and using the pony path. The first few metres up are on grass based surface, which zig zag up to the next gate. It’s quite steep and will involve ( probably ) some pushing. The path is clear enough to follow though. I was easily able to pick it up at the stile by the junction with the path to the summit on the way down.
Poor visibility on the moor would have thrown me out totally. I’d simply taken the os map and a compass, but as I said was able to see and overcome my error quite easily.