I’ve worked as an Election Judge 2-3 times over the years. It’s not very hard and it does reinforce the integrity of the system. I’ve always felt that vote fraud happens at City Hall, not at the precinct level, because it would be harder to do in secret at the precinct level with all those amateurs standing around.
Anyway, I worked a primary one time in a middle clas precinct where we had Republicans and Democrats on separate ballots so the voter had to declare which party they planned to vote for before they got to vote. I played “guess the party” as people walked in to vote and I found I was right 90% of the time. Republicans usually lined up in an orderly fashion, pleasant, neatly dressed with their voter registrations already out of their billfolds or available after the first request.
Democrats appeared annoyed-to-angry, often unkempt, never had their voter registration card ready for you, sometimes didn’t even have their voter registration card, and a few were already wearing “I VOTED” stickers on their clothing.
It was amazingly easy to tell much of the time who was who.
I’ve poll watched as well. You need scrutineers! Remember they can’t commit fraud if you’ve got eyes out there.