Your farrier wants peace and quiet. I could watch someone trim hooves all day; it's almost hypnotic. And yes, you're there to chaperone the horses at their regularly-scheduled pedi. But here's where the nail salon analogy ends.
Your farrier most likely wants to shoot the breeze, get the work done and get on with their life. Shoot the breeze does not include being a therapist for venting about barn drama, or any other kind of drama. You can chat, converse, but don't dump on them. How do you know if you're dumping? If your diatribe lasts longer than two hooves, you're dumping. If your monologue could be described as a rant, you're dumping. If the subject matter is something you'd prefer they'd not repeat but you're hollering loud enough the horse thinks he's being chewed out, you're dumping.
I'm not saying you have to be this happy:
That's Newt Gingrich's wife, by the way. I think my achieving that expression of frozen euphoria would require a trip to the derm AND the pharmacy. Merry Christmas to me!