My car has been clean nearly every day!
Ahhhh- the hose...forgot that detail...I use this-
http://www.shipstore.com/ss/html/ASM/ASMMRT50.html
It is a flat hose with a reel that squeezes out the water once you are done- Make sure you wind it up within a few minutes of finishing or the water will start to freeze in the hose. If this starts to happen and slush starts to come out while winding...you have to flush water through fast with the noozle off- and then wind it up right away.
The key to not having the hose freeze is to keep the water moving through it the whole time. Never let it sit without water flowing for more than 5 minutes.
I have one of those "Keys" that lets you turn on faucets that take that special key to open. There is always a university nearby with those faucets- which are there for watering the lawn. I have found lots of them that are not turned off for the winter.
I also have filled old laundy giant size jugs with water and used this. I use rechargeable d-batteries.
http://www.safetycentral.com/baoppososh.html
this one- is a little more crazy
http://www.zodi.com/
they have 12 volt versions as well as the battery version. There are also adapters for garden hoses.
These are the over the top ones.
http://www.hazmatshower.com/haz_hottap.html
, and I think if you can fill a bunch of old laundry jugs you are better off with that. Keep the jugs inside the car- they will radiate heat as well. Don't use Gerry jugs as they get to be too squishy to manage when filled with hot water. You don't need hot water for anything but the final rinse anyhow- this heats up the panels so they can be dried- much of the warmer water instantly steams off anyhow.
The key is to do the roof first spraying from the middle line down one side of the car- and try to do that side next immediately before that side ices. You have to have a good noozle like the ace hardware one with lots of spray selection. I use "Jet " setting to de-ice and get off the mud, then "Center" to do the rims and undercarriage, then "Shower" to do the sides of the car.
Since sun is limited- try to face your car towards the sun as the shady side will ice first.
You get pretty good at it once you know how your car ices. I can do mine in about 20 minutes.
Where are you in Boston? I could show you next time I wash my car.