Weekday bus transportation to Jinshanling

I will not be able to travel there on the weekend, so I need to take the bus from Dongzhimen to Miyun and transfer to a local bus at Miyun, or else take the long-distance bus to Chengde and get off at the Jinshanling intersection and probably walk to the wall. Which of these routes is faster? How far is it from the intersection on the Chengde highway to the wall? If going through Miyun is faster, what is the bus number from Dongzhimen to Miyun? Where would I find the tourist bus in Miyun, and how often does it run? Is there a number for the Chengde bus? Where would I find schedules for these buses? (I can read Chinese.) Thanks!