Front + proper foot retention as mentioned above OR front + rear

Skid stopping is quite ineffective even if you have the lower body strength to pull off masterful sick skids. Sure your wheels may have stopped rotating and you're skidding as a result but altogether the mass of yourself and your bike is still in motion.
A prevalent real world example supporting this is the advent and wide spread use of ABS anti-locking brakes in modern vehicles as a safety feature. Grip>skidding