How to decelerate effectively with a rear brake?
Yes, there's a technique, however I strongly recommend you to fix the front brake. Rear only is dangerous.
The rear wheel tends to block much sooner than the front one because of reasons you mentioned in the question so the obvious way is to avoid blocking as much as possible. First, you can emulate ABS on the car by quickly pressing and releasing brakes in series, this way the wheel will likely block, but with less tendency to slide sideways.
Another is moving your mass center towards back while braking - not cool, but it helps, actually.
And again - fix the brakes, repairing them is not a hard job.