I have been around for a long time. Some of you know me.
Here is my point of view.
Any show that has participant judging is for fun.
Plain and simple. Don't take it as a reflection of your car.
Even local shows. A 99% rare tan 4 door will get beat by a clean red convertible.
That's how participant judging works. People pick what they want to take home.
I have judged many nation events over the years.
It takes an average of 20 minutes to an hour on each car or more depending on the show.
The judges in these cases are judging specific cars they have real knowledge on. The car is judged against a set of standards not against another car.
As stated above. If you have specific work done a sign is a good idea then your peers can read what you have done and might be drawn in to look at it. When they see the workmanship they may be impressed and it may get you ballots.