Hide, Cloak, Toggle Confidentiail Fields

In 5.2, what are good ways to "hide" or enable toggling on/off sensitive fields, like "Cost" for Products?
I found "Hide controls on Add/Edit pages, based on logged user name" in the Help, but couldn't make anything of it.
I was thinking of showing the field only on the Edit screen somewhere in the middle, where the staff could quickly pick it out, even if a client were standing there, they probably wouldn't catch it.
What else applies in this scenario? I am thinking about shortening the session durations, too. Where is that done?
Thanks!