Them using pictures stating they are the ones detailing the car, thats a grey area...yes they are working on it, but if they are another business entity, I wouldnt allow it. If they are an employee, let them brag to their friends on facebook about the Ferrari they are waxing. If they are soliciting business from it, then I would ask that they not do it
I have a guy I work with more often these days and he posts pics and states he is helping me out. He doesnt claim them as his job or his client which I respect and have no problem with...
non-competes take care of them starting their own business after they are taught to do things your way.
In California, you have to give them business equity in order to enforce it....I.E a % of the business like 1-5%. Otherwise, in CA, non-competes are not legal to enforce.