When I joined the Critics Group I was given a number of singing exercises to learn to help with different technical problems - Wagner for small and unusual intervals, Galway Races (1 verse and 1 chorus sung in 1 breath) for breath control and a Gilbert and Sullivan piece, The Duties of the Minister of State (or a piece of mouth music), for articulation.
It took very little effort to learn them, and a little longer to master them so I could sing them well enough for the purpose they were intended.
The G and S sorted out my somewhat sloppy diction almost immediately and 40 years later all of them are still of use.
Jim Carroll