Yeah so the only way I have found to fill my LS and get all the air out is through the upper rad hose. I just disconnect it and fill it. Of course this should only be needed when filling for the first time or maybe if you have an air pocket.
But also, if you have a overflow tank connected to radiator, this should take the air out for you as you run the engine(so long as coolant is moving through the water pump and thermostat. So I like to run mine without the cap on it first so I can see the thermostat open and water pumping/moving into the upper rad hose(looking through the filler cap hole. When I see water flowing I know I'm good because that means eventually if there is still any air in the engine it's gonna push out as water is moving and via heat cycles. Shouldn't take but one or two drives with engine getting to temp for it to bleed.
I also have a driveway with a slight slope to it and I park with my engine uphill to bring all the air to highest point.
But mainly, the overflow is gonna really assist in bleeding/re-filling the radiator after the cap is back on and your driving around. Hot air will force its way out. You can see in my pics I have a temporary coolant overflow connected(1 gallon water jug, redneck baby
). I also only use distilled water only until I get everything where I want it in case I have to drain the system again. I will add antifreeze later.
You may already know all this
.