Cook the highest temp/doneness first. Drop the water temp to the next level and drop in the next steak. Then drop the temp again and add the next batch.
Time for each section of the cook will depend largely on the thickness of your steaks. The folk who developed this method for cooking steak to a variety of tastes suggest a minimum at 1 hour at each temperature, but this wouldn't be long enough with steaks 2 inch thick or more. I'd be looking at an absolute minimum of 2 hours at each temperature stop before cooling the water and adding the next issue of steak.
The idea is that, by the time the last steaks have been in the bath for their full duration, all steaks are at serving temp and can be removed, dried and finished ready for service at the same time.