The problem with water outside right now is that it is in the solid state, it's around 0F or something. I've done 55's in place, mix up a couple gallons of the bleach/water mix, and pour it in the tank. I use paper towels, as I always have them handy, to slosh the mix up the sides of the tank, wiping as I go. Don't forget under the rim, I like to do the outside of the top rim as well.
Siphon as much as the mix out as you can, if you get any of this in your mouth your teeth get so clean that they squeak. You can tip the remaining half gallon or so into a tub or shower, you can then put the tank on end in the tub or shower, and rinse.
If it is a tank that has to remain in place, sop the rest of the bleach mix out with old towels, fill the tank up with water, using about 5 times the dechlorinator you usually would. Let this run with an air stone, or filter with the media removed, for 24 hours. Drain after 24 hours, and treat is as you would any new tank.