I too, get a lot of window shoppers. I live in an upper middle-class town, and work in town at a full-time job. I often take the opportunity to talk with my customers there about what I also do on the side. A lot of people are interested, a lot of people take my card, but unfortunately, 1 out of 5 people probably pull the trigger.
Now, if I wasn't trapped in my workspace, and could show them pictures of my work, or take them outside, show them my car and look at their car - I might get that to 2 out of 5.
I also lose many peoples attention at the price. Mind you, I try to stay on the cheaper side, not because of less quality or pride in my work, but I'm not a 'pro' and I am still very young (20). A lot of people see me and doubt my abilities.
How could I avoid this and rake in the money? Better advertising, being able to show why the price is worth it, so on and so forth. It is a lot more difficult for those of us with a day job than those who solely rely on detailing for income. Personally, I work 40-50 hours a week at my job, and I'd rather not lose my 1st or even 2nd day off sometimes. I have a dog to care for, who I miss 40-50 hours a week. I have errands to run, and a social life. Take all of that into account, and you've maybe 10 hours for a car. I usually take that, and do a 'production' detail. No buffing, just a basic interior and exterior package. Gets a good $100 - $150. That's gas and groceries right there. Now I can use my other income for other bills, and maybe have some left over.
Basically, what I'm trying to say, (I ran off for a bit there) is that don't be worried if you're not getting many who actually use you. Just keep doing what you're doing, assuming it's the right thing, and show people what you're capable of. Earn their respect, and earn potential life long clients. Friendships even. That is far more worth it than getting every person I talk to about detailing to use my services. If that were the case, I'd have no time in the day for anyone or anything. Once a month detail is fine with me, and with two kids, I'd hope it would be okay for you. They'll appreciate it!