Draining gas tank

One way to do it – at least with carbed sleds, not sure about EFI – is to disconnect the fuel line before the fuel pump and run a length of hose to your catch can, then use an air hose to put pressure in the fuel tank. That will drain the fuel line. You don't need (or want) much pressure; I think some people just use a blow chuck and seal off the filler neck with their hand. You could also modify a fuel cap or make some kind of plug to attach the air hose to, making sure you don't apply more than a few PSI.

Siphoning is another option, one I'd guess will leave a bit more fuel in the tank. It's very difficult to get the tank bone dry regardless. Depending on the tank, even taking it off and dumping it may not get it all out. I prefer to fill my tank with ethanol-free gas (probably most critical) and add fuel stabilizer before I store it. I've never had a problem doing that. The good gas will keep a long time provided it's not exposed to much moisture or open to the air. It also gives you the option of firing your sled up every month or so, which probably does more good than any amount of fogging, draining, etc. I try to do that with mine, but often forget or am gone for an extended period – still no issues though.

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.