Lou, you might have already done this if you are concerned about air, but if not, try removing the temperature sending unit when you are filling the system. That will allow all of the air trapped inside the engine to purge through the top of the head while you are filling it. Put the fitting back in when coolant starts to flow through the hole.

Be sure that your valve cover is attached with a good gasket when you do this. If not, when the coolant weeps from the sensor hole it will flow into the exposed head. Don't ask me how I know this!!

Some guys will drill a 1/8" hole through the thermostat flange to allow trapped air to escape. I prefer to use ones with a jiggle pin that allows air to escape but also acts as a check valve to not allow coolant to flow through the air hole. The last 180 and 160 thermostats that I bought at Autozone (their Duralast store brand) both had jiggle pins.

Matt