You are in a tough situation for sure. There are so many rules for each of those classes you descibe and its hard to answer them all “correctly” as its really up to the individual judge…
I do totally get where you are coming from and I’m sure you will do a great job judging. Its tough in Canada as we don’t have a lot of drivers or shows. We always have to travel to the US to find some big driving shows.
For turnout classes, its usually just trot on the rail as soon as the drivers head in, counter clockwise. There is usually a ring person at the gate directing “traffic” ensuring everyones safety. So hopefully the show will provide you one of those. The judge is usually in the middle of the ring on the long wall and watching everyone as they enter.
They ask for a slow trot, working trot and extended trot both ways of the ring and then usually a walk across the diagonal. This way you can see everyones turnout at the walk as they go right past you (the judge). Once you have seen all the gates on the rail, they ask everyone to line up in the middle. The judge then goes to each individual and looks over the harness to ensure everything is in the keepers, nothing is on the last or first hole, brass is clean, bits are clean, people and grooms (if there is one) are clean and appropriate for the turnout. They sometimes ask to see a spares kit - should have a halter per animal, cooler per animal and a lead rope per animal as well, plus of course the spares kit with all the tools in it. If a carriage has breaks it could be a tie breaker. Our phaeton has breaks and we have lost several classes because of it. I get it, but dont agree with it Then they ask for a rein back. Look at the overall picture of clothing. Is it appropriate to the carriage (country turnout, formal turnout etc). Do they stand out too much? Too much colour/missmatch or not enough colour? I only say that as my husband got that comment on his last turnout class. Bay ponies, dark blue carriage, dark blue apron, black jacket, yellow tie. The judge did not like all the dark colours but did like his tie and shirt. We looked at the pictures and totally agreed with her! We went out and bought a new beige apron and will change to a grey jacket. Things to work on! Heres a picture of our old turnout so you can see. I find it easier for women as we can play more with colour. Remember - if its an EC sanctioned show, all drivers and grooms must wear helmets. They cant wear top hats or anything else. As a judge, you just have to overlook the helmet. We have had to show with our helmets in several Quebec shows this year. So I would say that 70% is based on the overall “looks” of everything. Harness fit, spares kit completness, cothing etc. The other 30% would be the working part of it. I have never had to do an individual test in a turnout class.
For reinsmanship - its pretty much the same as turnout. But you can ask for an individual test at the end. We have done our “normal” working trot, slow trot, extended trot, walk both ways. Sometimes a halt is thrown in on the rail as well. Then everyone lines up along the short side of the ring so there’s lot of room to perform a test. Then usually the announcer will say the test - our last one was perform a figure 8, halt, back up and salute, then return to line. Its up to the driver to decide how they want to do this, but they need to understand what they have to do. So you may get a few questions lol! We have also had to do a one handed circle, pick up both reins at the close of the circle, return to the rail, extend the trot down one side and then halt. Salute. Then return to the line up at a slow trot. Test is totally up to you! We have also done classes where there has been no test and its all judged on the rail. Its all about how the person holds the lines, posture etc. Judged like an equatation class.
Working class is similar to the turnout class but is judged on the animal. How they work, how their gates are. If a pair, how well do they work together and how well are they matched - even pulling etc.
Hope this helps!