So how can I get more confident with the Westie Cut then?
I would say go to Championship Shows and see what correct Westies, Airedales, Bichons, Cavaliers, Lhasa/Shih Tzu, Cockers should look like. You can then adapt the trim to a more manageable length for a pet dog, but the ‘look’ and shape should be the same. If you’ve been taught to put clippers on Cockers/Westies backs, you’ll see why they don’t look the same as the breed standard. :'(
I remember trying to recommend a training school when you were looking because it’s so easy for places to take your money and set you free without sufficient training and backup for you to start on your own. :-\