Buses do not run between resorts, unless the resorts are on the same route....for example, BW buses will also stop at the Swan and the Dophin and sometimes the YC/BC.
Your only option, using Disney transport, is to take the bus directly to Ecpot from CBR.
You could take the bus to DHS and then either walk (15-20 mins) to WS from there, or take the boat (25 mins not including wait times) from DHS to WS.
You could also take a cab from CBR to BC and then walk to the International Gateway (entrance to WS), takes about 5 mins to walk from BC.
I would just take the bus to the front of Epcot.