If your motorized dish isn't aligned properly, skew will be the least of the problems. If its not on the arc, you won't get anything from many (most or even all) of the satellites. Everything lines up perfectly on a motorized setup as long as your LNB skew is set to '0' and the motor/dish assembly is aligned on the arc.
You don't really have to find your true south satellite if you use USALS; In fact, you may not even have a satellite at true south. For example, I live at 90.1 degrees west longitude. There is no bird there, my closest south satellite is at 91w. Using USALS, however, I can instruct my motor to go to any satellite close to my true south location (for example, 91w, 93w, 89w, etc.), and align the dish on that bird. It all works out the same... When my motor is exactly at '0', the dish is pointed at 90.1 degrees west (there's nothing there). It moves a little bit to the west of '0' to hit 91w, as instructed by USALS.