Danny I agree with you on the petcock being that prime and on are the same.
Although I disagree with "and let it run out of gas on it’s own". This is not only bad for the motor (from what I have been told by my mechanic every time I run out of gas, and he comes to the rescue). It is actually worse to leave the carburetor empty of gas. Gas by its nature repels water, leaving gas in the bowl will in fact keep rust from occurring in the carb or anywhere else for that matter. The lack of gas causes condensation (water) to form on the inside of the carb and will cause oxidation (rust) of all the parts. If you have ever noticed when a metal gas tank starts to rust it does so from the top down, not the other way around, that is because there is less gas at the top of the tank more often, thus allowing condensation and oxidation to occur more often.
If your going to store something use stable, either that or go and start it about once a month and let it idle for about 15 minuets. Either method will keep rust and gumb (caused but the gelling of gas) from building up in your carb.