Well, if it were me, I'd take however many cans of gas you think it'll take, add stabilizer to the cans, fill them, and top it off. You'd probably be just adding the recommended dose of stabilizer based on tank size and fill it with plain gas. The only time I'd say an additive won't mix in enough is if you just dump it in without adding gas, or if the tank is close to full. Adding stabilizer to the gas can, filling the can at the pump, and then filling the sled will give you the most thorough mixing. With a relatively empty tank though, it probably makes no difference.
It would be nice to run it long enough to get the stabilized gas through the fuel lines, though not necessary. What I like to do warm it up, then shut off the gas to burn up the fuel in the carbs and fuel pump. That's more of a "may help a little" thing though; probably the best way to avoid any potential issues is to pull the carbs when you're getting ready next season. Take the bowls off, spray them down with carb cleaner, and blow out all the passages. Maybe overkill for a sled that's you've owned a while and taken care of, but I'd recommend it for one that's new to you so you can be sure it's clean, and verify your jetting.