I had the worst time filling the coolant on my Grand Prix... What I found that worked best is
  1. take off the upper heater hose and leave open
  2. With the rad cap off start filling the overflow bottle and once the coolant reaches a certain level it'll start to run into the radiator.
  3. Fill slow until coolant comes out the heater hose fitting.
  4. Put the heater hose on and open the bleeder screw on the top of the thermostat.
  5. Fill untill coolant comes out there.
  6. Put cap on and fill up the coolant reservoir.
  7. Start car and it'll usually purge the rest of the system out... Add coolant as needed..


so Far after 3-4 times of doing this on a couple different times it has worked flawlessly everytime.. I usually run the car for 5mins or so and check the heater temp out of the vents.. If it isn't warm you have a air pocket... If this is the problem you need to stop - cool vehicle and repeat.

I didn't see any fill procedures posted but maybe I missed it...