easy to clean the snow off of your car. First turn the defroster on with heat, brush the soft snow off if it's too thick, than bring a gallon of regular water "not hot" and pour on a car all the snow and frost will be clean with before you know it.
Not a very good suggestion when average temperatures are -20C...because if you pour water it will freeze before it is cleared...:-)
And for your first 2 suggestions one has to know first which is their car and if they can open the door and turn on defroster...unless of course some one has advanced enough car that they can start defroster and such from their home....
No bro thats why I said turn the defroster on with heat and than brush off the snow first by the time your windshild and windows and the front of your car with engine heat will be warm so as you'll pour water it'll clean it. It's my personal experience.