I would think converting to brass with teflon coated ball would be the only surefire way.

I was going to suggest converting to a brass one too. I have a few tanks with them I use for work, they just have a simple on/off boiler cleanout valve on them and they work pretty easy provided they aren't frozen solid.

I keep a torch in the truck when I have then out in the winter, easy to unthaw if they do freeze up.

Silicone grease should help.



The thing you run into, or I do, is that dirt or ice will have roughed up the ball a tiny bit.



And it won't be really smooth.



Should make it workable though.



Might dismantle it as much as you can and spray silicone down into it, handle might come off or whatever.  Doubt it is rebuildable but even taking it off and spraying some inside to soak a bit on the ball while the hose fitting is upside down holding plenty of liquid lube might help out.



I have both spray silicone lube of some sort and a thicker actual grease.



If you don't have the spray or liquid taking it somewhere warm and getting the grease warm might help.