I think the key to it is educating people about the importance of detailing in winter - weekly vacuuming and proper washing (not at the swirl-o-matic), monthly waxing, etc. If you can sell your services more as protection for their investment, rather than just a "beauty service" for the rich, you're golden.
If you can work out a lift or ramps so that you have direct access to the undercarriage, thats a big selling point. Everyone I know loves to ask me what I do about undercarriages in the winter. I just blast em out, but having a lift might be a big selling point. Also, offer a spray wax on the undercarriage. Its just one of those things that I am willing to bet 90% of people are going to opt for, given the choice.
Also, point out how destructive salt can be on stuff. A nice conversation piece might be to go down to a junkyard, and pick up some sort of underbody piece that is completely destroyed by rust, and than pick up a similar one in nearly new condition. Have a sign that says "This one was protected with "XXXXXXX (name of product you like to use)"" and another that says "This one was not". Also have a kelly blue book, so you can point out the value difference between a car in "excellent" condition and one in "poor" condition.
As far as I've learned, education is the key to marketing. Most people neither know nor care how their negligence affects their second most expensive possession. If you can show them that your details are not only saving them money in the long run, they are also making their vehicles more enjoyable to use.
You want to teach them enough, but not too much. After all, you don't want them detailing their own cars
.
Best of luck
-Tim
