I made a thread a couple months ago when I attended a session run by Rob Buckland.
His advice was a 'Dah' sound should be your standard articulation. Nice open throat etc.
Then different phonetics for different types of accents.
You see you can't actually tongue 'harder' to accent as the tongue moving off the reed is what starts the note. It's either off or on.
a 'Lah' sound is a smoother almost legato tonguing effect.
'Ha' is a more aggressive tonguing etc.
If you sing tunes to yourself as if you were playing them it's like du, bee bo da, ba doodle da bee bo da (Moose the Mooche idea) kind of idea, these phonetics are making the accents. no one sings Moose the Mooche la, la la la, la lalala la la la.
You will notice the more aggresive phonetics like 'urgh' 'uh' and 'Ha' start much lower down near your lungs and lower throat. 'Tee' and 'Ta' start right at the front of your mouth and that gives a pretty rubbishy tone.
The lower down it starts the more it 'fills out' and the more control over the tone you have.
Try some of these and see what works for you.