I had my tractor tires filled with the Rimguard ("beat juice")
ballast. It was part of the purchase agreement and was done before the tractor was delivered. It was the only option my dealer offered, although they didn't preform the filling. They took the tractor to a local tire shop (no idea which one) and they did it.
I have taken the tires on and off my tractor a few times since owning it. Only once did I need help getting the tire back onto the hub. The key is to not let the tire fall over. Take it off the hub and lean it up against something sturdy. Lifting the tire back onto the studs is a real pain, but no impossible. A few blocks of wood, a long pipe or pry bar, and a delicate ballet of brute strength, and the tire will go back on.
As for what to put into the tires, you really cannot beat beat juice. It does not freeze in our temps, does not corrode, and does not cause harm to the environment if you puncture the tire. It's relatively inexpensive, and several tire shops around the country offer it.
But probably the most important aspect is, its freaking heavy! After all, thats what were after, the weight. Water is 8.34lbs per gallon, windshield washer fluid is lighter at ~7.6lbs per gallon, calcium chloride (definitely not recommended) is very heavy at 11.3lbs/gal but is horrible stuff, mixed with water, antifreeze is kind of heavy at ~9lbs/gal, and beat juice is right at 11lbs/gal. So, all things considered, beat juice is the way to go, in my opinion.