Two other guitarists in that same mold...Roy Clark and Jerry Reed. Most people know them from their various movies or TV shows, and don't appreciate just how great guitarists they were.
I was into jazz, blues and rock and never took notice of Campbell until late one night years ago he was on some TV show playing instrumentals, not his hits, and just tore it up. I gained a whole lot of respect for him after that. Same with Lyle Lovett. Both can/could play the hell out their six strings.
Roy Clark was so awesome, and Buck Owens could play, too!
And Hank Garland. Absolutely phenomenal.