As the PP said, they only run buses to the Epcot Resorts from DHS and Epcot when the boats have been grounded (due to thunderstorms) and after the boats stop running (boats stop going to a theme park one hour after park closes).
Otherwise, you can take the boat which goes: Epcot -> BW/BWV -> YC/BC/BCV -> S/D -> DHS -> S/D -> YC/BC/BCV -> BW/BWV -> Epcot.
It takes about 25 minutes to get from Epcot to DHS, once underway. It might be slightly longer depending on how long it takes at each stop. The boats depart about once every 15 minutes, but there is no set/posted schedule of arrival/departure times.
In terms of walking, it's about 1.2 miles from Epcot to DHS via the Boardwalk. It's about 1.3 miles from the YC dock to DHS, so that's about the same from BCV (because you'd probably head towards the BW first).
As the PP said, most times the BW/BWV shares with the S and D, while the YC and BC/BCV share a bus. There will be times when all five resorts are on the same bus, so it can get crowded fast.