Another good alternate idea is to have them put in the 'goody bag' if there is one.
Or have a table dedicated to flyers wherein everybody can take the ones that interest them...that way everybody at the show can see/choose, not just the participants.
This
Seen it at more then a few shows in WI
When you are registering your car for the show , paying , your already at the tables , have another table set up with all the flyers like mentioned
Our first local show is usually around the first weekend in May - Huge show if the weather is decent , have seen snow flakes more then once
Everyone and I mean everyone is there handing out flyers - One year I had over 50 in my car as I had left my car there and disappeared for awhile
Lesson learned on the windows - I don’t mind it , took five minutes to clean out , but didn’t look very good at a Car Show