This is such an excellent question!  

I try to identify the reason the tone has become airy or unfocused.   

1) It just hurts to play for the first day or two after each adjustment and especially when first getting braces--so it may be a lack of practice.  When there is pain, I give them lots of other things to do: Writing in and clapping and counting (or with beginners using cups to learn quarter note and eighth note rhythms.)  Finger and say scales or pieces, and then play.  Breathing exercises.  For bleeding I tell them to talk to their doctor to get those little wax strips.  The old wire type of braces are the worst. 

2) Now that the lips are more forward because of the braces, they need to get the air back down.  The Pneumo Pro is great to actually see where the air is going, and can be a quick fix.   I have them aim their air high toward their upper gums and them use upper lips to bounce the air downward.  Using a zombie face helps.

3) Patricia George suggests building up the lip plate with tape to make this angle easier.  I've never used this method...students have always been able to get their tone back.

4) I remind my students that when the braces come off, the adjustment will be easy and they will probably have even more flexibility than before having  the braces. 

I have a very recent story about braces, which is one of the most difficult experiences in my teaching practice.

On average, about 75-80% of my students get braces at some point and they usually adjust fairly quickly and their beautiful sound returns back in a short time.

However, this year I have a new student who has significant difficulties with the embouchure and the sound, mostly related to adjusting the hole, the jaw (which is naturally pushed back a little too much), the air direction and speed, also the student did not practice much, but finally she began to get a decent sound ... until one day came with braces... We lost all our work of several months 🤯🤦‍♀️ Improvement stopped, she completely lost her sound... We needed a new position, placing it much higher on the lower lip (my impression is that her braces are very thick inside and have changed the shape of her embouchure way too much) She also has a hard time to keep it in the right spot because it constantly hurts inside - it's really hard for her to get used to braces in general.

After a few weeks I ordered a Pneumo Pro for her and we started using it last week. Today she came to class, we started with long tones and she had a pretty good sound. It's incredible to go from no sound and unwillingness to put in any effort to adjust to a pretty good sound in just one week. From F3 and up, she still has some difficulty, but she can play. Today I almost cried from happiness 😅 The student looked happy, too!
Thank you, Kathy for your invention! In some cases this is a life saver!