The system is supposed to be self-bleeding through a vent hole in the thermostat housing. If you installed the thermostat correctly there may have been a small arrow at the top to indicate the place for the vent hole.

Assuming this was done, with the car cool, park it with the nose uphill, remove the radiator cap and run the car at a higher idle until it warms up, turn the heater on to full. This may help if there's trapped air.

Your heater issue may be related to the temperature, or not. It sounds like now it's working OK, though? Or does "hot at all times" mean now you can't regulate it?

Running hot and getting warmer at a stop may mean the fan clutch. Particularly if blipping the throttle and upping the engine speed causes the temps to drop. But how fast is "instantly"? That's got me confused. Does the needle swing, or gradually go down? Instant swings on a temp gauge don't sound like a temperature issue.