ArchLinux: Wrong keyboard and admin applications

[Cleverson Casarin Uliana]

Dear, I want to use a Portuguese keyboard with the Brazilian layout 
inside Gnome, but even after making sure it is selected over English, 
the layout remains other. It's a Dell Vostro machine with an USB 
standard keyboard. Do you have tips to help on this?

Also I'd like to implement a scheme similar to distros like Ubuntu, 
where you can change administrative settings and use admin applications 
like GParted while logged as a normal user, and Orca gives normal 
feedback as well. AFAIC, this is done using Policykit, but its page on 
the Arch wiki claims to be outdated, and anyways it sounds confusing to 
me. Can anyone please explain how it is done?

Thank you,
Cleverson