I always crack open the low point drains for a couple of seconds while the antifreeze is being sucked up to make sure there is pink stuff getting to that point, it also pushes out any water or air in the system.
Married To The Navigator
2005 Red GMC Duramax 4X4 HD Crew Cab
4" Magnaflow, Banks Air Intake
Firestone Ride Rite Air Springs