I'd do the following:

1. Ride north through the Prospect Park to Grand Army Plaza
2. Take Flatbush to Tillary
3. Left at Tillary
4. Right onto the Brooklyn Bridge on-ramp
5. Once off the bridge make left at Chambers
6. Cross the West Side Highway onto the Greenway
7. Exit at 26th Street
8. Make left at 8th
9. Right at 27th

Not the most bike friendly way since Flatbush can be hairy as is Chambers, but I used to ride that route often without incident.