I think for "brand explorer" you only need one stay at each brand. I have the "10 brand" explorer badge but only 7 brand-specific badges.
This is the "Brand Explorer Badge" (or may be better to call it the "uber brand explorer badge"):
As I indicated, unless someone else wants to pay the $750+/night x 2 nights/stays for any of the 4 currently open Editions or $400+/night x 2 nights/stays for two stays at some MVCs, I'm not gonna get that badge.
David