Assuming it is a posi, those procedures are correct.
If it is an open, only jack one side and leave the other tire on the ground. Rotate the tire, on the jacked side, one full revolution, counting the revolutions and partial revolutions of the driveshaft, double that amount, and that is your gear ratio.
So, for example if you counted 1 3/4 turns, you have a 3.55.