This is one of the biggest PITA jobs I do on any of my cars!

You are probably not revving high enough.  2000 rpm is a pretty good
clip, crank it up to the point where it sounds too fast and that will
probably be right!

Use a helper or a block of wood, etc. to hold the throttle open.  First,
open the bleed screw on the connection between the two large hoses above
the engine, and open the bleed on the radiator.  My bolt is a tight fit
that won't allow coolant out, so I have to remove it.  Then start it up
and rev to 2000 and add the 50-50 mix of coolant.  Get as much coolant
as possible in before you start it, then top up while running.  When the
coolant comes out of the radiator, replace the plug and put the cap on
the expansion tank before dropping the rpms.  Shut off engine and let
sit for a couple minutes and repeat the process.  Having fun yet?

Check the overflow/fill tank daily for a week and top up, small bubbles
will purge themselves out while you drive and coolant will be sucked in
to replace the air.

Have fun and don't scald yourself--coolant will gush out if you drop the
rpms before putting the cap on!

Stuart