Proper process is to loosen the pinch bolts on one side (I generally loosen the R/H side, opposite the speedo drive) while leaving the pinch bolts on the other side tight. Now take your 12mm drive of choice and loosen the axel bolt. You can use a 12mm hex key, but a 12mm drive bit on a 1/2" ratchet is a much better option -- significantly more torque. If you can use the drive bit on an impact wrench, so much the better. If the nut side turns when the axel is turned, then use your second driver to restrain it. You'll need the second driver for install torque any which way.