We did make it in 1 day, but it wasnt easy since we speak absolutely no chinese. Buses from Luoping to Kaiyuan were leaving at 7:50am and 10am on the Feb 17th, but on the 18th when we needed to go there was only 1 bus leaving at 12:40pm. So i am not sure if the schedule depends on the day of the week or even/odd days. Drive to Kaiyuan took 5 hours. Last bus from Kaiyuan to Yuanyang leaves at 13:40pm, so to make it you must be on 7:50am bus and hope for no traffic/accidents on the road. Morning buses start going around 7am I think. We hoped on the bus to Geiju, they were leaving when full, and we waited only ~10mins before it got on the way. It took ~1h to get there. Last bus from Geiju to Yuanyang leaves at 18:45pm, and we were 5 mins late for it. They told us to take a bus the next day, but then woman who was getting ppl for another bus, tried to explain there was a sleeper bus going somewhere far and passing through Yuanyang, and we managed to get on it and it dropped us of in Nansha. It left Geiju at 19:30pm and took abt 2 hours. No minivans/buses to Xinjie at that point, either sleep at Nansha (plenty of hotels near the bus station) or find a taxi to take you to Xinjie (they were quoting us 120-150RMB).
