After reading numerous methods on how to get air out of a automotive cooling system, came across this funnel. Seems like a good tool to have as long as it fits your car:

Looks like it will fit GM radiators.

I've never used one, so I don't know how well they work.

Best way I've found is install a tee fitting from the flush kits at the highest point in the heater hose and fill from there. Also makes draining faster, just open the petcock and turn the screw-on cap to release pressure.

Good idea. One thing to keep in mind is many of the GM OEM replacement radiators do not have petcocks- you to have pull the lower radiator hose to drain the coolant.....