With an automatic, just shut of the ignition. The steering will require some extra effort, but unless you are about to go around a curve, it shouldn’t be too much of a challenge. This practice experience was part of drivers education back when. Stopping just using the emergency brake was also practiced.
bttt
My husband as a teenage driver took an off ramp from the freeway and his brakes failed right before the hard turn, he threw it into reverse and stopped!