Back when I opened a wash in the 90’s, the ICA had small bifold pamphlets that we handed out to customers. If I remember, it was about the benefits of professional washing over driveway washing.
You could probably outline whatever it is you would like your customers to know, and get a professional looking product from Kinkos or some other print shop - there are many services online these days for professional printing services in bulk.
With where we are now with technology and smartphones, you might convey information to your customers more readily with some downloadable pdf file that can be scanned or linked to a website that you maintain.
I’m kinda in the middle. I use my phone for stuff, but I still like paper too and like having a pamphlet or brochure for things.