No, you do not need to do a Judge training. There is a short tutorial that opens for Judges once they open their unique ballot.
Depending on your event, you may want to do a Judge training to explain to Judges how to interview Competitors, or what to look for in a Competitor, but that is at your discretion.
We recommend setting up a demo event for yourself to really see what it's going to be like! You can also check out the Judge Experience Video here.