[Dixielandjazz] bass(tuba) line for slow tunes

[Jim Franz]

New to dixie/trad jazz w/45 years of playing what's on the page. 
Getting by on faster tunes, but slow tunes, especially Louis Armstrong tunes like Kiss to Build A Deam On, and When It's Sleepy time Down South - I am lost trying to play a decent bass line. Many recordings I can barely make out that there is a bass line, let alone hear it. 
Since so many tuba players answered the recent head-count, I wanted to ask how a tuba player learns to play a slow interesting bass line. 
Jim Franz