Well the flush seems to have worked, was 29* this morning and it heated up much better than it has in the last two years. Not sure if it's 100% or more like 85% now but it's plenty until I can screw up the courage to change the heater core and most likely the head and head gasket too. Been hearing water rushing sounds from the heater core area still unfortunately and I think it might be combustion gasses not an air pocket. Oh well it is still much better for now. Maybe I can tear it down in summer for that rebuild.