I have put filtered/de-oiled second-hand AF from junkyards in my farm tractor tires for decades since the traditional calcium chloride is so corrosive it rots the rims out with the slightest leak in a tube or valve stem in a matter of a few years .. Of course we do this for tractive weight, not balance..
A fairly-new practice for farmers and construction is BEET JUICE for ballast .. Maybe you could try that instead of AF for balancing your tires, it's biodegradable and supposedly will not freeze.. I have even thought about using waste vegetable oil . As for special tools, there is something called a "water valve" that can be bought at any Tractor Supply chain store or similar .. They have a 3/4" water hose connection and screw onto the valve stem, and an air vent for the obvious reason