Hi Mark,
The method I have been using since household refrigerators has increased is as follows. I am not a big fan of pumping the non-toxic pink antifreeze thru the fresh water system although highly effective. Since the icemaker water solenoid is difficult to get to, I've been using compressed air to purge the solenoid and water line. You can purchase or fabricate an air inlet fitting that attaches to your city water inlet connection. Pressurize the system to 75 psi. Cycle the icemaker harvester a couple of times. You will know when it happens because the pressure will drop to zero. This method is also effective on other difficult items to winterize such as toilet water valves, exterior showers, pressure washers and washer/dryers.
Hope this helps, Fred