Since you recognize the brands are registered in each county is your problem not knowing where your GG grandfather lived? Have you tried to locate him in the 1880 census? That might give you a lead to his county of residence. If that takes you back before he was an adult, you might try the 1900 census. At least you could determine from his children;s ages and place of birth at least what state he lived at different periods in time.
If you know when and where in Texas he was born it might be a starting point because many of the young men started work fairly close to home. If you don't know, perhaps a copy of his death certificate might help, Texas began keeping such records in 1903.
Your public library probably has a copy of a book titled "Texas Cattle Brands" compiled by Gus L. Ford. It doesn't pretend to be a complete record of Texas Brands but it is well done and has a lot of information.