Dear Steve Wright,
Thanks for contacting Top China Travel!
Travelling to glass bridge at Shiniuzhai National Park from Changsha is quite easy. Shiniuzhai National Park is about 180 kilometers away at the eastnorth of Changsha. It takes about 2.5 hours by car from Changsha. There are a few buses passing by Shiniuzhai National Park from Chang East Bus Station. But you need to check the bus schdule by yourself.
If you miss the direct buses, do not worry, you can transfer via other places to get there, such as Changshou(长寿), Pingjiang(平江), Longmen(龙门), etc. If you depart from Changsha in the early morning, you can return in one day, no need to stay overnight there.
Of course, if you drive there by yourself, or rent a car through travel agent to take you there, it is more convenient.
You can travel by train to Yueyang, stay overnight, and then take transport from there. But this is no neccesary, as Yueyang is about 190 from kilometers downtown to Shiniuzhai National Park, farther than Changsha.
Any further request or question, please feel free to contact with us.