3 years on and I'm trying to focus on just one "Billy Barlow". I'm dealing with his story.
However, I can't help finding bits and pieces that fit with my 13-year study of the whole BB thing.
Here goes:
1. "...stuck in the mud like Billy Barlow". I now have many references to this line, mostly from here in Australia and from New Zealand. Up to the 1870s. The latest comes from just west of where I live. It seems the line was used whenever a town-council was a bit tardy about fixing a road. Or when there was a flood. All of these post-date the line from the American Civil War soldier mentioned above. NB he says it's "childhood's memory". The line must come from a song popular enough to easily slip into public consciousness.

2. A friend tells me that, in his part of Victoria, Australia, "a bit of a Billy Barlow" -- said of a particular type of character --is still part of race-track cant.

3. "Little Billy Barlow". Just found a reference to this title as given to my current subject of study. It comes from his performances in Aberdeen in the 1840s. Did he sing a song containing this line in Australia? Is that why I heard it as a song-fragment, in Forbes?

Watch this space. All further ideas and links welcome.
Cheers, Joy