Well, it depends on how cold it gets in Tennessee (I've never been there, so don't have a clue). In the Pacific Northwest it rarely gets below 40 degrees. I bought some fish-friendly car wash at greenhome.com and plan on washing the car in the driveway: rinsing, soaping it up, letting it sit for five minutes, rinse and chamois. On rainy days (just about each day I've washed the car there have been off and on showers) I've backed it in the garage for the chamoising and waxing.
Until the car wash arrived, I took it to a local drive-in car wash, where they had a do-it-yourself wash bay. Problem was, buckets and chamoising weren't allowed; I could only use the soap in the pressure washer.
The last wash I took off the wheel skirts and cleaned the inside of them, and the wheels.
I think some people have mentioned going through a touchless car wash, wheel skirts off.
EDIT: There is a long thread with explicit details on how we all SHOULD be washing our Insights--with Meguiar's, three mitts, clay bars, etc. The wash techique and schedule a couple of the Moderators keep is a bit daunting. :lol:
Car washes are a bad subject with me. The absolute best commercial car wash you'll find is going to be a 3 star one, most are probably 1 star. Any car wash with anything that touches you car is going to be full of contaminants. Think of it, a muddy truck goes through before you, do they do anything to clean that dirt off of their equipment before they touch your car? Grind! These should be avoided. Then there is the touchles car wash. With these you avoid scratches, but they have to use fairly harsh chemicals to get your car clean.
Unfortunately your best bet is to clean it ourself, that way you know you do everything in your power to avoid scratching. I would say maybe figure out a way to mix some water from your hot water heater with your cold tap water and maybe that would help. From what I've gathered from the people at Meguiar's online they just brave the freezing cold and wash their cars as quickly as possible.
In my are, winters are eratic between a solid freeze for only a few days to a couple of weeks at a time, to melting temps just above freezing point, for remainder. Lots of salt, dirt, & melted snow marks. During winter months I only use the self-serve spray washes as I am paranoid about brushes grabbing the wheel skirts and the fastening system is a pain even when the fingers are not freezing! I always look forward to the spring! This will be winter #4.
In winter I use touchless car washes.
They don't do a great job at cleaning the car perfectly but they do a good job of removing most of the salt, dirt and other contaminates to protect the paint and reduce corrosion on the steel parts.