I utilize a portfolio of before and after photos when talking to a potential client. The photos speak for themselves.
In addition, after walking down a vehicle I'll try to explain what my products and service can do for their vehicle's particular problem. Then I'll explain why higher quality products are the best option for the work and the consequence of using inferior products.
Lastly, I try to educate and build common ground. One thing common is, most folks like a clean car and think it takes a long time along with hard, sweaty work. I'll eliminate that hard work for them (building value for my service). I'll get there car back to better than showroom (more value building). I try to use terms and product names that are common. Everyone has at least heard of a Meguiar's product. I explain while Meguiar's products are great I don't use too many OTC Megs, or I've replaced a Meguiar's product with a boutique type product (not that its required I just like to use them, Klasse AIO for example). I mention all that to show how I'm different than the local shops the use a basic OTC cleaner wax. This builds even more value and hopefully back up why I charge a little more than the local shops. That seems to interest folks. I've done the research to find the best products for my services. People see value in that.
That's how I used to run my small business. I've since closed down my small business and moved to a new state. In the new area, I've only shown a few pics of my work and people have seen my ride. I could be booked up right now, but I'm taking it slow. I'm not trying to get too busy.
Good luck