Exterior/Express Washes - How Do You Promote Express Detailing

Would like to hear from exterior/express car washes about their express detailing programs:

a. How do you promote sales?
b. What services do you offer?
c. What percentage of your car wash volume purchase a service?
d. How long did it take you to arrive at that percentage from the time you
started offering the services?
e. What are your prices?
f. Including the wash or not?

Thanks in advance for your information

Bud Abraham