I've never had air in the cooling system. After draining the old coolant, I pour a 50/50 mixture into the radiator slowly until I see it above the radiator core, then with the cap off, I start the engine and monitor the temperature gauge and watch for movement in the coolant. When the thermostat opens, the coolant level will drop in the radiator upper tank, then I add more 50/50 mixture in very slowly until it's about 1/4 inch from the top of the tank. When it stabilizes at that level, then install the radiator cap. Never had air in the system.
I'm not even sure htat this is a problem. Just annoying. The gurgle happens only when the RPMs go up then it stops when the acceleration stops. Do you know which hose from the engine goes to which entry on the heater core?