On mine there is usually a bit of standing water that will dry out given the opportunity. Seems like a good idea to let it all dry out. Air is going to get in there when you drain the tank and air and moisture left in there will cause corrosion. I just like the idea of letting it dry out.
"The less air that gets in the tank when it's empty the less corrosion will occur." Not sure I totally agree with that unless you're purged the air to begin with. Hey, JMO.
And I use a dab of anti-corrosion paste on the threads of the anode rod.
I usually use a piece of foam or something malleable that is breathable but keeps the bugs out.