If you need to unlock your phone to show someone, unlock the day 2 day account.
It's not fool proof but might fool someone who is not aware of the feature.
That said, the cops will probably not take a smartphone without contents at face value. You've got to add some realistic enough (fake?) texts at least, or be careful to only communicate about protests, homosexuality and other banned subjects through your alternative user account.
Unless you have something to hide, trying to mislead armed officers of an authoritarian regime this way may not be advisable. They'd probably be fooled by simply carrying around a second phone, though, because most people only carry around a single phone. Do your revolutionary talk through an old banged-up second hand device, and talk about other stuff using your fancy phone.