Using Airlift UView 5500 question

[mikesz]

I recently replaced my water pump, thermostat, and front engine mount. I had drained the coolant by removing the hose to the thermostat and waterpump. I put it all back together and added a couple of gallons of FRESH pre-mixed prestone anti-freeze, silicate free, phosphate free, etc. I realize 2 gallons will NOT completely fill the system. I was going to use the Burp method to purge air from system but decided to purchase a UVIEW airlift 5500 system. I have seen the youtube video. I was wondering will it still work if the system is partially filled with coolant? Should I drain what is in the system, use the Airlift system then re-fill again using the Airlift system once it has vacuum?