I have a thought. Sellers - let people look through your stuff for a minute before you start your patter. Read the room. If a buyer wants to ask questions about the rusty manifold in the milk crate or talk about the ford his grandad sold cheap, let him start the conversation, but please don't jump on him the second he enters your area.
Please remember that most people are browsing.
Edit: - So happy that the Portland Swap Meet is on again this year after a two year pandemic hiatus.
http://portlandswapmeet.com/