"Just say Toh."
Jim DeSano would say that to me all the time in lessons. Between that and "Are you keeping your corners down?" Would become phrases I would hear over and over and over for four years. It eventually stuck. When ever I get into trouble with the horn, the very first thing I check is to make sure I'm using a 'toh' syllable. More often than not, my embouchure may have slightly warped and thats why the notes aren't working, or an articulation sounds sloppy, etc.
So we should establish first that there is a preferred syllable for playing a low brass instrument. 'Toh' is another god to add to your growing pantheon of musical gods (but first and foremost, thou shalt not sin against the metronome.) 'Toh' gives us a clean attack with a warm body of sound. On occasion, when going into the upper parts of your register, you can think more of a 'too' articulation to help keep the embouchure small and compact for the small but fast air column. What say ye about softer articulations? 'Doh' and 'Loh' are great options.
Okay, what sounds to use are pretty easy to outline. But how do you get better at these articulations? How do we make improvements? By practicing these articulations of course! Below I've included some ways to break down and work on your articulations. These are also great in improving consistency in your time (exercises should have multiple purposes, efficient use of time.)
This exercise is great at helping isolate and letting the musician focus on the air and the articulation. If a particular lick is giving you trouble, you can take a page out of the Engelkes Collection of Rules & Ideas: play the troublesome lick on a single repeated note, and focus on just air and articulation. More often than not, if a lick isn't quite lining up right, the articulation has gotten funky and needs ironing out. Another exercise to remember:
Very simple, therefore also difficult exercise. Working on playing consistently with a 'doh' or 'loh' articulation on this, and work it everyday. You won't see improvement right away, but a week or two in, you'll notice your slurring consistency will be improving.
Well, there you have it. Articulation in a nutshell.
Jk, but get into the practice room and start using these and you'll see improvement in the near future!