Use a metronome. Set it to MM=60.
1. Do this as a breath exercise.
2. Do it as a buzz exercise with glissando. Slide from note to note.
Take in air on count 4 (after breathing mark) and close lip with "UP". Start the buzz with a POO attack. Do it very soft. Try to use the same feeling as when doing it as a breathing exercise (1).
3. Do it with legato and centered tones.
4. Do it with TOO attack and without legato.