I would expect your second approach to work:
What problems are you seeing with it?
To avoid manually listing ten (or hundreds) of fields, try Smakovskiy's clever approach suggested at the end of his document on this very subject:
Well, he's not declaring the set in a variable. It's just a complicated set analysis expression. But if you can't get it to work by manually listing the fields, his approach won't work either, as it's just a way of automatically listing the same fields.
Is it possible to post a small sample application demonstrating the problem with the manual approach? You might be able to do that by reducing the data in your real application if you can't come up with a simple, fake example. You can also scramble any sensitive information as required. Hopefully it'll be easy to see what's going wrong if we have something to look at.