One thing I have learned in getting results from people....is to work to help them succeed....not prep them for failure.
I make sure I am clear, articulate and thorough and so long as they are working hard, trying and being conscientious...I have all the patience in the world to help them get it right and learn something perhaps.
If they de-rail and start improvising, talking through their hat... or move into the 'know-it-all' lane...then I become a difficult customer, and I do it very quickly.
Remember a lot of these kids working these counters are your kids....many of them are the current generation, and for most of them...that is all they have been shown, taught or exposed to.
Remember there are know-it-all older guy/geysers that are often looking for a fight too, just waiting and hoping to correct or 'trap' someone with some tiny nugget of their own knowledge or experience that they should just put on the table up front.....lol.
All good
Coley