My new-brass "prep" consists of (1) pushing the necks over an expander ball or similar tool, to remove any dents and make sure they're round
(2) Measure to see if the cases aren't longer than the specified maximum length. If they aren't, I chamfer them. If they are, I trim and chamfer.
I have mentioned many times before that sizing new cases is almost always a waste of time, and make make them worse: If you resize in a typical expander-ball die, the expander may pull the neck out alignment with the case body. Generally, new brass is very straight, because it's formed in a die WITHOUT an expander ball. But an awful lot of handloaders apparently believe that brass factories don't know how to form cases correctly.
