The Maddox brothers and Rose were known for doing manic tunes, just have a listen to Ugly and Slouchy, they never copied anybody and always did things their way even down to the slapping bass sound which they was the first to do, yes they invented slapping the bass...
They was not drunk, it was their way of being different.
The double bass player, who played the bass in that song, could slap it well. For those who do not know what slapping is: it is pluck its strings, and then the string would "vibrate" and hit the fret board on its own. If that happens, you would hear a slap sound.