Most of us, by now, use a tool that vacuums down the cooling system for easy filling. If not, get one. It's such a time saver especially on those that are tough to bleed the air out of.
But here's the tip; Ever had the case where you just can't vacuum the system down and dread the fact that you'll have to take the extra steps to fill it up and then pressure test to find the source of the leak?