A couple more thoughts from the peanut gallery now that we have more info.
I don't worry as much about air in the parts of the cooling system as I would frozen sea water. But, if you really want to keep the cooling system pickled, you could place a funnel full of antifreeze on a short piece of hose on top of the raw water pump intake so that as you spin the motor by hand, antifreeze that gets pumped out into the muffler gets replaced...again, remembering to drain that extra antifreeze from the muffler so it doesn't have a chance to backfill up the short hot stack on our C-30's when you
do restart it next time.