Steven Meade came out with a couple of play-along books, which came out with a CD to play with that are helpful. Each track allowed you to switch back and forth to each part. I've found it challenging and it also broke up the monotony of the Arban and other technique books.
Also, playing in a small ensemble, like a tuba quartet, broke things up too. With small groups there is "no where to hide" and is a challenge to dial in some of the techniques you develop when practicing alone. When playing with my tuba quartet, I've discovered some my own areas I need to work on by myself. It has helped in advancing and making me a better player- keeping me out of the 'ruts'. Just a thought.
Euphs:
Miraphone 5050 Ambassador
Wessex Travel (Tornister) Euphonium 'Maly' ER154
Yamaha 201 Baritone
Mp: Wick SM4 Ultra X
Groups:
The San Diego Concert Band