I remember when I was still an unbaptized publisher going from door to door. I also remember when I found out about this whole cart witnessing thing and was told that each person has to be approved in order to 'participate'... I couldn't help but wonder, 'What the heck are the qualifications'?
Having that said, in my career as a publisher, I had a few opportunities to 'participate' in cart witnessing. I wasn't approved, but those opportunities were really outcomes of certain circumstances, such as when I was doing door-to-door preaching with somebody who had already planned cart witnessing afterwards but couldn't drive me back home. (I was younger at the time, without the driver's license.)
I think it happened around three times. It was the best type of preaching, precisely because I didn't have to talk to anyone. I was still inexperienced, yet I didn't have any problems with cart witnessing...
Those 'qualifications' are really a joke, I'd have to say.