Winterize Water Softener System

My coach has a water softener system installed when new by RV dealer not Newmar. It also has a water filter attached to the panel that I believe was done at Newmar. My concerns when winterizing is to insure the water filter housing and the softener system are both winterized.

To fill my coach I use a water line that comes from the side/top of compartment. Then there is another line that comes from the top of compartment and attaches to the fresh water inlet on the panel.

The previous owner believes the water softener will be winterized with antifreeze from the pump just like the faucets. That will be the case if it is in the pressurized loop after the pump. I believe the water is going through the water softener first then to the tank (to fill) or the water system if the city water line is hooked up.

There is a small spigot on one of the water softeners so I may be able to drain the water but wonder if the lines need purged. The other container I believe holds the salt so don't know if that needs antifreeze. If I can't figure out a simple way to winterize then I will be a water pump and use it to force antifreeze through the fresh water inlet hose (that feeds the softener).

Thanks