Cold turkey is a method of adaptation. It includes jumping straight to a desired polyphasic schedule without extra steps, unlike the other methods.
This method so far is the most popular, since the adaptation takes much less time than a gradual adaptation. The difficulty overall is somewhat higher compared to a gradual transition due to the instant reduction in sleep time.
For a goal schedule, which reduces only 1-2 hours of sleep, cold turkey is the most ideal method.
Schedules with a lower total sleep time usually have gradual adaptation routes. This is a possible alternative to cold turkey. Although, such route takes much more time, often months to reach the final schedule.
With enough preparation and an effective alarm system, cold turkey should be a sufficient method of adaptation to most schedules.